facebook_pixel

Category Archives for "SCUBA Gear"

How Do You Read The Markings On A SCUBA Tank?

By Jose Cernuda

Understanding the Markings on Your SCUBA Tank

Have you ever wondered what all those markings on your SCUBA tank mean? Many people don't know it, but many of the markings that go on SCUBA cylinders are required by law. In the United States, the Department of Transportation regulates SCUBA cylinders. In Canada, it's Transport Canada that regulates SCUBA cylinders. Every country has their own regulatory authority so these two are just examples. 

On most SCUBA tanks the engravings on the shoulder will  indicate the following:

  • Manufacturer
  • The serial number of the cylinder
  • The material the cylinder is made out of (steel or aluminum)
  • Tank capacity (how many cubic feet or liters does the tank hold)
  • Service Pressure (what amount of pressure the tank can be filled to)
  • Original Hydrostatic date (this tells you the age of the cylinder)
  • Department of Transportation or other regulatory markings certifying that the cylinder has passed certain minimum requirements set by the government

Below is an example of markings you’d find engraved on a Luxfer aluminum 80 and next to it an explanation of what the markings mean.

Illustration of the engravings on a luxfer aluminum 80

There are many different possible engravings a cylinder can have depending on the manufacturer's it’s specifications and what part of the world the tank was produced. Because of this, the following chart contains common engravings found on different SCUBA cylinders and what the engravings mean.

Engraving Meaning
184Cylinders service pressure expressed in BAR
207Cylinders service pressure expressed in BAR
230Cylinders service pressure expressed in BAR
237Cylinders service pressure expressed in BAR
2400Cylinders service pressure expressed in PSI
3000Cylinders service pressure expressed in PSI
3300Cylinders service pressure expressed in PSI
3442Cylinders service pressure expressed in PSI
"+"indicates cylinder can be overfilled by 10% when placed next to hydro date
01A20An example of a hydrostatic exam date (numbers will reflect the date)
3AMolybdenum Steel
3AAMolybdenum Steel
3AL U.S. specification for 3-gauge aluminum
3ALMCanadian specification for 3-gauge aluminum
AIndependent Inspector Mark
Catalina Cylinder Manufacturer
DOTDepartment of Transportation (Cylinder passed U.S. specifications)
FaberCylinder Manufacturer
HPIndicated High pressure (3300 to 3500 PSI)
LPIndicates low pressure (2250 to 2400 PSI)
LP95Model Number (also Indicates "low pressure" 95 cubic feet)
Luxfer Cylinder Manufacturer
M9542DOT Manufacturer facility number
P869232An example of a serial number
S040 Model Number (also Indicates 40 cubic feet)
S080Model Number (also indicates 80 cubic feet)
SU7694Canadian special permit number
TC Transport Canada (Cylinder passed Canadian specifications)
TP5250Test procedure for hydrostatic retest (PSI)
XS-80 Cylinder manufacturer and model number (80 cubic feet)

The above list doesn’t show every possible marking. Also, things like model numbers, dates, serial numbers, etc. will vary from tank to tank. In the list above those markings are shown as examples since the actual marking will change with every tank.  

Also, it's important to know that even though the model number will often indicate the cylinder capacity, you should still look up the manufacturer specs when it comes to this. As an example, a Luxfer S080 is typically marketed and referred to as an 80 cubic foot. This number, however, is rounded up. The cylinder actually contains 77.4 cubic feet. You can see the specifications for the most common tanks here

Hydrostatic Testing Stamps

Another common engraving found on SCUBA cylinders is the hydrostatic test date. Many people simply refer to this as the hydro date. The original hydrostatic exam is usually found on the shoulder of the tank together with the other manufacturer engravings and tells you when the cylinder was originally manufactured. SCUBA tanks need to be hydrostatically tested every 5 years. Subsequent stamps are usually somewhere in the shoulder area, but you may need to look around. I've seen stamps in pretty much every location you can think of on a SCUBA cylinder.

Visual Inspection Stickers

Close up of a visual inspection sticker on a SCUBA tank

Visual inspection stickers are another marking you'll commonly find on SCUBA tanks. While obviously not an engraving visual inspection stickers provide useful information about the cylinder. They tell you when the last inspection was performed and whether or not the cylinder has been cleaned for use with Nitrox. 

Nitrox SCUBA Tanks

It's very common to see tanks designated for use with Nitrox. This is usually done with a sticker rather than an engraving. Nitrox tanks are labeled for two reasons. First, so that everyone knows that the tank contains a gas other than air. This way no one will accidentally dive with a tank that they do not know the contents of. Nitrox requires the use of different decompression tables than air and the added oxygen also presents different risks that divers need to be aware of. Second, because Nitrox tanks are often filled with pure oxygen and then topped off with air as part of a partial pressure fill, the tanks need to be cleaned for oxygen. Technically, it's the visual inspection sticker that tells the technician filling the tank that it's clean, but the big Nitrox sticker is also helpful.

Any SCUBA cylinder can be adapted for diving with Nitrox. Most new SCUBA tanks come ready to be filled with Nitrox from the factory. However, if you are purchasing a used cylinder, you may need to have your local dive shop clean the tank and for use with Nitrox along with changing the O-rings to Viton O-rings so that they are compatible with Nitrox. Once this process is completed, the dive shop will indicate that it is safe for Nitrox on the visual inspection sticker. Additionally, many shops will place a Nitrox sticker on the tank to indicate that the cylinder may contain a gas other than air.

Recommended SCUBA Cylinders

Choosing a cylinder that’s right for you involves looking at many factors. Among those factors are:

  • Your breathing rate,
  • Body size
  • Planned diving depth
  • The mix you’re using
  • Your body's buoyancy characteristics
  • How you trim out in the water with your current configuration
  • How much gas you’d like to have in reserve at the end of the dive

These are all factors that go into deciding what SCUBA tank will be best for you. We have an article that goes in-depth into this topic here.

For more information on specific cylinders, we recommend you check with the cylinder manufacturers directly. The “additional resources” tab below contains links to the cylinder manufacturers listed above. You can find information that goes beyond the SCUBA tank size chart there. 

Additional Resources on SCUBA Cylinders

The SCUBA Diver’s Guide To Choosing The Perfect Diving Drysuit

By Carlos Sagaro

If you ever considered whether a SCUBA diving drysuit is right for you, you came to the right place.  You’ve probably spent some time wondering what the best drysuit is or the what the differences are between a wetsuit and a drysuit are when you are in the water. We know that deciding whether to go dry can be both confusing and scary but stick around because in this article we are going to answer a ton of your drysuit diving questions and steer you in the right direction in your quest to determine whether or not you should dive dry.
Diving Drysuit diver in cave

What Is Drysuit Diving

Drysuit diving is SCUBA diving with a suit that keeps water out thus ensuring that you do not get wet when you are in the water.  The drysuit works by holding water out and maintaining watertight seals around the neck and wrists.  Because water conducts heat 25 times faster than air, having a layer between you and the water will keep you warm.  Drysuits keep the water out completely

Many divers have a misconception of the actual purpose of a drysuit.  See, they are not really designed to keep you warm.  While some do provide some thermal protection on their own (we’ll tackle this a little further on in this article), their main purpose is to keep a diver dry.  While this can be counterintuitive, after all, we all know our wetsuits keep us warm, drysuits are not great at thermal protection on their own.

But, how does a drysuit keep a diver warm?  They achieve optimal thermal protection when they are used with an undergarment.  It's the undergarment that keeps you warm. The drysuit is there to keep the undergarment dry. Drysuit undergarments are designed to be worn underneath the suit and the pieces of equipment that provide thermal protection.  We discuss undergarments with more detail a little further down.

Why Go Drysuit Diving?

Drysuits open up an underwater world that would not necessarily be available to divers who do not use them.  Divers use drysuits to dive in the some of the coldest water on our beautiful, blue marble.  They are also worn by divers who are going to be diving for extended periods of time.

It’s not always about diving in really cold water. I use a drysuit when I dive in the Florida Springs. The water temperature there is about 72 degrees Fahrenheit (22 degrees Celsius) year-round. You’ll see people with no exposure protection whatsoever swimming there. However, since I cave dive there, I’ll be underwater for prolonged periods of time. I could probably get away with diving in a wetsuit, but the drysuit provides comfort by keeping me warm throughout the entire dive. It also makes it much more comfortable when I exit the water because I am already dry and do not need to rush to change out of a wet wetsuit.

By keeping the diver dry, the drysuit allows the diver to maintain body heat over a longer period of time. Without a drysuit not only would diving in colder water be extremely uncomfortable, it could also lead to hypothermia, a dangerous condition which occurs when you lose too much body heat.

How Cold Can You Dive in a Drysuit

People routinely use drysuits to dive under ice. So as long as the water hasn’t completely frozen over yet, and provided that you are using the correct suit and undergarment, you can use them to dive in waters as cold as 34 degrees Fahrenheit (1 degree Celsius).

Diving Drysuit diving in ICE

Whether in the artic, Antarctic, beneath an ice-covered lake near a mountain in Russia, in the freezing waters of the cost of the American North East, or off the coast of the cold waters of the UK, the proper drysuit and undergarment can keep you warm enough to enjoy this otherwise inaccessible underwater world.

Diving Drysuit Divers in mountain lake (1)

How is Drysuit Diving Different than Diving in a Wetsuit?

By now you know that drysuits work very differently than wetsuits. Wetsuits keep you warm by keeping the water that is inside the wetsuit and close to your skin at a warmer temperature than the water you are diving in. They keep you completely dry.

Because you are completely dry you now have to be concerned with an extra air space while diving. Because your body is completely sealed inside the drysuit the space inside the suit creates an air space. This air space if not managed properly can become dangerous.

Suit Squeeze

As divers, we know that because of Boyle’s law gasses will compress as we descend. The air space inside your drysuit is no exception. If gas is not added to the suit as you descend underwater the suit will compress around your body to the point that moving will become difficult. It can even cut off your circulation and cause bruising due to how tightly a suit can compress around you.

For this reason, all drysuits have an inflation valve (usually in the front) so that the diver can add air as he or she descends into the water.

Diving Drysuit Inflator
Diving Drysuit Dump Vavle
Dump Valves

Similar to the way that you need to add air to your suit as you descend, you also need to dump air from your suit as you ascend. This is the same as managing the air space in your BCD wing. In order to dump air from your suit, it will likely have at least one dump valve usually positioned on the upper arm (below the shoulder).

Managing the Additional Air Space

Much of learning to dive dry is about learning how to properly add gas to your suit while descending and dump gas from it while ascending. It can be trickier than it sounds. Too much gas will throw off your buoyancy. It can also create a bubble inside your suit which can travel around as you shift positions. This is something you want to avoid!

If you have too much gas inside your suit and the extra gas makes its way towards your feet, it can cause a dangerous situation where you become inverted in your suit. Because there are no dump valves near your feet you may begin to ascend uncontrollably towards the surface feet first.

This is why you may want to consider a drysuit course or at the very least learning to dive dry from an experienced and qualified instructor.

Suit Flooding

Another thing that’s different about drysuits is that you have to consider the possibility of a it flooding. If one of the seals become compromised or your suit tears during the dive it may become flooded with water. In very cold waters this can be dangerous. It’s also why drysuit undergarments need to be made from a material which will keep you warm even when wet. This means you can’t just throw on a cotton sweater and jogging pants underneath your suit.

Drysuit Buoyancy Considerations

Drysuits are generally more buoyant than wetsuits. How much more will depend on the suit material and the undergarments being used.

You’ll need to account for this difference in buoyancy by either adding more weight to your SCUBA diving rig, using a stainless steel backplate to add weight to your rig, or using a SCUBA tank that is more negative than the one you use while diving wet.

In order to determine the correct amount of ballast, you should perform a buoyancy check in the drysuit using the undergarments you intend to dive with. Note, changing your undergarments may change your buoyancy requirements in a drysuit.

Drysuits and your BCD

Because drysuits hold an additional air space some people wonder if they can replace a BCD? The answer is NO! The airspace is the suit is not as easy to control as the one in your BCD. It’s also not designed to balance you out in the water. You should never rely on your drysuit alone for buoyancy. Some divers consider a them a redundant form of buoyancy control should your BCD wing fail. While in an emergency this may be possible it is less than ideal.

What are drysuits made of?

Drysuits come in several different materials.  Neoprene, crushed neoprene, vulcanized rubber, and trilaminate are some of the most common.  The most popular of these is trilaminate and neoprene.

Vulcanized Rubber

Vulcanized Rubber Diving Drysuit

Vulcanized rubber suits are more often used in commercial settings and are not very common for recreational or technical diving. Some of the early drysuits were made of this material, but more modern materials have made these suits rare in the diving community.

Neoprene, Crushed Neoprene and Compressed Neoprene

Neoprene suits are made of the same material as your wetsuit except that they are designed to hold an air pocket between you and the outside rather than a layer of water.  The main benefit of neoprene suits is that they provide some inherent thermal protection on their own.  Still, you will need to use an undergarment in colder water or on longer dives.

Neoprene Diving Drysuit

If you decide to go with neoprene, there are a few things you will need to consider.  First, neoprene suits require the diver to add more weight.  This is especially true towards the end of your dives when you are performing safety stops at shallower depths while breathing out of a tank that is less full. 

They tend to be harder to put on than trilaminate suits and take much longer to dry.  This is important because they must be stored completely dry.  If you will be travelling, they are harder to fold and weigh more.

Finally, you’ll need to decide between a neoprene, crushed neoprene or compressed neoprene suit. The difference is that “compressed” and “crushed” neoprene take an existing neoprene material and using heat and compression compress the material so that it won’t compress as much underwater as you dive deeper. This makes it so the buoyancy characteristics of the suit won’t change throughout the dive. It also makes the neoprene more durable than that of a wetsuit. Different manufacturers use different processes to create their versions of crushed or compressed neoprene so it may be difficult to compare one brand to another.

Trilaminate Diving Drysuit

Membrane Drysuits

Membrane drysuits have become much more popular for recreational and technical diving. Most membrane suits are made out of a trilaminate material. The terms membrane and trilaminate are used interchangeably by most in the dive industry. The trilaminate suits are made out of two to three layers of durable material. The outside is usually a nylon, polyester or Kevlar material.  There is usually a butyl rubber membrane in the middle.  They are extremely durable and easier to patch than neoprene suits.  They are also more resistant to deterioration over time.

These suits offer some benefits that have made them more sought after. They are much less buoyant than their neoprene cousins.  They are easier to put on and take off than the neoprene suits, and they are easier to move around in than their neoprene cousins.  They are not as positively buoyant as neoprene so they will not require as much ballast.

Trilaminate suits also allow you to layer as much or as little undergarment material as needed depending on the diving conditions. This makes them ideal for both cold and warm water diving. They also dry much faster and are easier to fold for travel.  On the other hand, they offer little to no thermal protection so you will have to use an undergarment with them. 

The Parts That Make Up Your Drysuit

You already know that most drysuits will be either a membrane / trilaminate material or some form of neoprene, crushed neoprene or compressed neoprene. You also know that that the suit will need to have an inflator and a dump valve to manage the air space inside. Below are some of the parts of the suit that you need to know about when looking at and considering different types of suits.

Drysuit Seals

Diving Drysuit Wrist Seal
Drysuit Neck Seal

The seals of the drysuit are designed to keep air in and hold water out.  There are two types of seals: Neoprene and latex.  Neoprene seals are less expensive to replace than latex by are a little difficult to slide through.  If you purchase your own suit, you can trim the seals as needed.  This allows you to create a more comfortable fit.

The most common material for drysuit seals is latex. If you happen to be allergic to latex, silicone seals are also available. The problem with all seals is that eventually they will all tear.  When a seal tears, you’ll need to have it professionally re-installed since it is attached directly to the suit.

Many manufacturers make “wrist rings” or “Zip seals” which allow the diver to change out the seal themselves. With these systems, the seals are attached to a ring which in turn is attached to the drysuit. The seal attaches using a system that is similar to that of a zip lock bag. The advantage of this type of system is that, should a seal tear, you can repair it yourself on the fly.

The disadvantage of these systems is that the ring makes the suit a little bulkier around the ring where the seals attach. Also, because it uses a seal that is similar to that of a zip lock bag it’s possible for this seal to become undone and allow water to enter the suit.

Drysuit Zippers

The zipper is an extremely important part of your suit.  Aside from being the most expensive part of the suit to replace, it requires regular maintenance.  You should wax your drysuit zipper as recommended by the drysuit manufacturer with the recommended wax.  Apply the wax on the outside of the teeth so that you do no gum up the inner sealing surfaces of the zipper. This is not a place to skimp.  A dry suit sipper can cost 300 to 500 dollars to replace.  Also, if it breaks, it ruins your diving day and even future dives as they must be repaired by a professional.

Diving Drysuit Zipper Closed
Diving Drysuit Zipper open

The zipper position is another thing that you will have to consider when buying your drysuit.  The zippers can be positioned across your shoulders, in the front, or on the back of your suit.  I recommend you try on a few and see which you prefer.  I like the front zipper because I can zip up the suit myself. 

When zipping your suit, do not yank hard on the zipper.  Zippers are extremely sturdy, but they can break.  Make sure to treat them as gently as possible. Stretch the zipper out as much as possible and steadily pull on the zipper until it closes.

Knee and Elbow Pads

Over the years the knees and elbows of many suits tend to get worn down the most since these areas tend to rub the most while getting ready to go diving. Many suits reinforce these areas with pads. With many suits this may be an option only available with the more premium models, but it is something worth considering.

Drysuit Boots

There are several options when it comes to the boots of your drysuit. Some suits come with the boots already sewn into the suit itself. Others come with a sock-like foot cover allowing you to place a boot on top of the sock. The boot is sometimes referred to as a “rock boot”.

The advantage of having the boot be a part of the suit is that it is streamlined and allows you to use a larger variety of fins. The disadvantage is that if the boot wears out, you’ll need to have it replaced professionally.

Diving Drysuit Boot

The advantage of a rock boot that fits over a sock like finish is that you can easily swap out boots when they become worn out. The disadvantage is that rock boots tend to be bulkier and sometimes the foot pockets of the same fin you use with a simple bootie when diving wet may not fit as comfortably. This may mean you need to get a fin with a larger foot pocket to use with your drysuit.

Drysuit Suspenders

Suspenders are a feature which many drysuits have. The suspenders make it easier for you to put on your drysuit. They also allow you to wear your drysuit with the top part off while you are on the surface and preparing to dive. This makes it more comfortable when the air temperature is not as cold and you don’t necessarily want to have the entire suit on.

Diving Drysuit Suspenders

Drysuit Gloves

Diving Drysuit Gloves
Diving Drysuit Mittens

If you will be diving in cold environments, you may need to dive with dry gloves as well. The gloves like the suit are water-tight keeping your hands dry throughout the dive.

Dry gloves can either be worn over your existing wrist seals or they can be connected to an attachment ring or zip seal if your suit has that option. Dry gloves come in gloves, mitts and three finger mitts. Mitts and three finger mitts are the warmest option, but you lose dexterity with these options.

Whatever option you choose, you should try it out before diving. Make sure you can reach and unclip any equipment you use during the dive and purge your regulator with the gloves on.

Drysuit Hood

The hood you wear with your drysuit is an important part of staying warm underwater. The hoods are typically made out of neoprene and work the same way that wetsuits do. It’s extremely important to try on the hood and make sure it’s a snug fit. It’s also important that it doesn’t fit too tightly around your neck since it can put pressure on the carotid artery, causing a reflex which slows the heart resulting in poor oxygen delivery to the brain. This can cause light headedness and even unconsciousness. This can also happen if neck seals that are too tight!

The Dump Valve’s Position

As mentioned previously, most manufacturers position their dump valves just below the shoulder.  This position allows you to move your arm to ease dumping air when you are in a full horizontal as well as a vertical position.  This is the best position because it does not require you to contort your body into awkward positions to dump gas from your suit.

Please note that there are a few dry suits manufacturers that position the dump valves higher on the shoulder, but this is not recommended as it makes it more difficult to dump air depending on your position in the water.

Diving Drysuit Dump Valve position

Please note that there are a few dry suits manufacturers that position the dump valves higher on the shoulder, but this is not recommended as it makes it more difficult to dump air depending on your position in the water.

Fitting your Drysuit

This is of paramount importance.  It is imperative that you try on the dry suit you are planning on purchasing before you buy it.  One thing to also note is that you should try the suit on with the undergarments that you plan on diving with.  This is crucial to determining proper fit. Different manufacturers cut their suits differently so a medium from one manufacturer may be a large with a different manufacturer.

Diving Dry suit fit

The drysuit should allow you to have full range of motion when you are diving.  Make sure you can reach your valves should you need to perform an emergency shut off. Also make certain that you have as close to full range of motion as possible.  If your suit does not fit properly, you will never be comfortable when wearing it which will make you enjoy your diving less and add to stress load when underwater.  It can also create a dangerous situation because you possibly could not be able to reach your equipment easily or at all. 

Off the Rack Vs. Custom-Tailored Suits

It is possible to get a dry suit custom made for you.  Manufacturers will have you measure your body is several different points depending on their specific measuring guidelines.  They will then tailor a suit to fit you specifically. 

The benefits here are many.  The suit will fit you better which will allow for better movement in the water.  This will reduce or even eliminate restrictions in movement which will provide much more comfort.  A better fitting suit will have better buoyancy characteristics because it will be less likely to create air pockets.  This will make it easier for you to maintain neutral buoyancy and trim when diving. You can add gear pockets wherever you like (more on this later). 

One of the factors that should be taken into account when making this decision in the price.  Custom fitted suits are more expensive than their off-the-rack counterparts.  A drysuit is a big investment and purchasing a custom fit suit adds to the expense.

The drysuit should allow you to have full range of motion when you are diving.  Make sure you can reach your valves should you need to perform an emergency shut off. Also make certain that you have as close to full range of motion as possible.  If your suit does not fit properly, you will never be comfortable when wearing it which will make you enjoy your diving less and add to stress load when underwater.  It can also create a dangerous situation because you possibly could not be able to reach your equipment easily or at all. 

Drysuit Undergarments materials

There are two things all undergarment materials have in common. First, they are designed to keep you warm. Second, they need to be able to keep you warm even if they become wet. Keep in mind that a drysuit is always in danger of having its seals compromised. For this reason, whatever you wear under your it has to be able to keep you warm even if it becomes wet.

A drysuit undergarment is designed to be worn underneath your suit while maintaining warmth.  Without them, you will lose body heat rather quickly rendering your drysuit useless.  Undergarments are an essential part of every drysuit.  A great tip to remember is that undergarments can be layered.  Anyone who has been in cold weather knows that layering is an excellent way to keep warm.  This same concept applies to your drysuit underwear.

Drysuit Undergarments are made of several different materials.  

Thermal under

Thermal Undergarment

Drysuit Loft Undergarment

Loft Undergarment

Diving Drysuit Fleece Undergarment

Fleece Undergarment

Fleece undergarments are designed to be soft.  This material is very comfortable.  Fleece undergarments are great as a base layer in your drysuit arsenal. Fleece also has a tendency to wick moisture off of the body which is good should you sweat of should you have a small leak in your dry suit.  Another aspect of these that make them popular is that they are smaller, so they are easy to take with you when you travel.

Merino Wool is known for its ability to maintain body temperature well.  This is specifically designed to repel water on the outside while absorbing it when worn against the skin.  The benefit here is that it will not get soaked should your suit leak while wicking away sweat from your body.

Loft undergarments resemble the same material used for sleeping bags.  As the name suggests, these undergarments are thicker and are excellent at maintaining body heat in freezing waters. Due to their design, it is recommended to wear a base layer that wicks away sweat so that you do not feel wet while diving.

The question is, which undergarment will you need?  It truly depends on the temperature of the water that you are diving in.  Undergarments are measured by their thickness which is measured in grams.  There is a range of thicknesses available and each manufacturer will spell out the recommended water temperatures for the corresponding undergarment.  It is also a good idea to contact local divers who are familiar with the area where you intend to dive to see what they have been using and what they recommend.

Accessories for Drysuits

There are many accessories that you can purchase to personalize your drysuit.  What you decide to buy wholly depends on your preferences and needs when you are underwater.

Drysuit Pockets

Pockets can be either installed by the manufacturer or can be purchased and glued on by the diver. The pockets will often that have D-rings inside them to attach equipment. You can use clips on your gear, so you do not inadvertently lose you gear when you reach inside. The pockets are usually placed on the thigh on either side of the body or both depending on your needs.

Diving Drysuit Pocket

Heated Vests

If you want additional warmth without additional layers you may be interested in a heated vest. The vest is worn underneath the suit and needs to be connected to an external battery.  It is important to note that, should you decide that you want to add a heated vest, you will need to add a connection that allows you to connect the battery to the vest you are wearing underneath.  Some divers even carry more than one battery with them should they be on a long dive and the first battery runs out of power.

Pee Valves

Diving Drysuit Pee vlave hose
Drysuit Pee valve

Pee Valves are an option for drysuits as well.  These allow you to urinate with your dry suit on. These are typically used when you will be doing longer dives. You will have to attach a connecter to the suit that then attaches to a condom catheter that attaches to the penis.  For women there are internal catheters as well as an external one.  This will allow you to pee when you are diving and is an option to consider if you are going to go on long dives.  The valve itself is connected to a rubber hose which then connects to the end of the catheter. 

It is highly recommended that you follow the instructions of the specific pee valve you purchase to properly learn how to use the pee valve.  If you are going to use a pee valve then we recommend that you add a pee valve to your dry suit when you purchase it.  It is not an expensive thing to add and you can always decide not to use it.  It is better to have it and not need it and installing one later will end up costing you more.

Argon Bottles

Some divers, especially in the technical diving community choose to have a separate cylinder dedicated to inflating the drysuit. When a separate cylinder is used Argon is usually the gas of choice. Argon has a lower thermal conductivity than air or nitrox, so it helps keep the diver warmer during the dive. Because argon can be dangerous if inhaled, the cylinder used to contain this gas need to be clearly marked as containing argon and only used for this purpose.

Drysuit Gaiters

As mentioned earlier one of the tricky parts about learning to dive dry is avoiding putting too much gas into your suit. The most dangerous part about having too much gas in your suit is if you allow that gas to travel to your feet. Drysuit gaiters are wraps that go around the lower part of your legs (around your calves) in order to avoid gas traveling to that part of the suit. The gaiters can even be built into the suit as a feature. While this can help beginner divers still getting accustomed to a dry suit our recommendation is to learn to put the correct amount of gas in your suit and the maneuvers necessary to empty gas from your feet if it should happen. Gaiters are really a crutch that shouldn’t be relied on in the long term.

Alterations

One of the greatest benefits of drysuits is that they can be altered to fit your body better. This allows you to achieve greater comfort over the long run.  Of course, this can only be done if you own the dry suit.  You can cut the seals to ensure a better fit.  You can change the boots depending on whether you prefer one type boot over another.  You can even shorten the sleeves and legs of a suit.  You can even change from dry gloves to wet gloves.  Lastly, you can purchase a suit that is custom fit for your body.  Be aware that custom suits do cost more but the investment may be worth your while if you intend on using your suit often.

Dry Suit Maintenance

Dry suits do require regular maintenance to maintain proper function.  Also, regularly maintaining your drysuit will ensure that it lasts longer. 

Seal maintenance is vital.  Make sure to be careful when donning and doffing your suit that you are not wearing jewelry or hair ties.  Watch to make sure that you do not dig your nails into the seals when you stretch them out.  Check for splitting or cracking of the seals and have that attended to before your dive. 

The zipper is the most expensive part of the suit to repair.  Make sure you store it in the open position and regularly lubricate it with wax to maintain its integrity.

A poorly maintained dry suit will not last as long as one that is properly taken care of.  More importantly, drysuit failure can be very dangerous.  Because your drysuit is being used to keep you comfortable in very cold water, a failure can lead to an emergency situation.  If your suit fails while you are underwater, you can suffer form hypothermia.  This can make It more difficult for you to decompress, focus, and function.  It can even cause buoyancy problems.

Make sure to rinse you suit well after each dive, especially in saltwater.  Make sure you hang your suit so that it can dry properly before storing it long term.  A properly kept and maintained drysuit will last you for years and provide excellent performance throughout its service life.

Drysuit Training

One of the most common questions that we are asked is “should I get training to dive a drysuit.”  The short answer here is “yes!”  While diving in a drysuit is not as hard as you may think, it does offer its own set of circumstances that can be acclimated to much more easily if you are properly trained.

Diving Drysuit divers traning

I remember the first time I dove dry.  I had my own misconceptions as to how it would feel.  I was worried about things like: I am going to feel squeezed?  Will it be hard to move?  Will I be able to reach my valves in an emergency?  What if I end up “feet up” in the water? Is this thing going to stay dry?  The truth is that none of those things were warranted.  If you properly adjust the air in your suit, you will not feel squeezed.  A properly fitting suit does not restrict movement.  And, yes, my suit did keep me dry!  All my fears of diving in a drysuit were not very warranted.

With that said, there are a few things that you need to know.  How to react in an emergency situation.  How your drysuit will affect your trim and buoyancy, how much more weight you will need?  Proper training will address all those things and much more. 

It is important to note that an overly filled drysuit will make it difficult to maintain trim and buoyancy.  Your drysuit does have positive buoyancy but should not be used for primary buoyancy compensation.  It can be used in an emergency situation but, aside from that, you should only add as much air into your drysuit as you will need to keep it comfortable and prevent a drysuit squeeze.

In time and with proper training, your drysuit will feel as natural underwater as your wetsuit does. This is why it’s important that you find a qualified instructor if it’s your first time diving in a drysuit!

In Conclusion

So, you probably came into this wondering “should I get a drysuit?”  I hope that the information in this article has helped you get a better grasp of what owning a drysuit entails. 

Whether or not you should dive dry ultimately depends on the type of diving you’re doing and how cold you get while you are doing it.  In the end, diving dry can be as natural as diving wet once you get used to doing it.  Practice and experience make all the difference.

If you do decide that a diving drysuit  is for you, you should get assistance from a professional dive shop. They can help you in choosing a suit that fits you properly, choosing the correct undergarments and even help with training so that you remain safe.

Did we miss anything about drysuit diving?  Have any questions?  Please comment below and let us know!

Want to Learn more?  Below are some recommended articles where you can find out more about Diving Drysuits.

SCUBA Cylinder Specifications

By Jose Cernuda

The chart below contains SCUBA cylinder specifications in both the imperial and metric systems of measurement. This chart is a compilation from many sources. It is intended to be a starting point for comparing different SCUBA tanks, their capacities, dimensions, weight, and buoyancy characteristics. You can go directly to the sources used in compiling this list by clicking on the “additional resources” tab at the bottom of this page.

SCUBA Tank Size Chart

  • Imperial

  • Metric

ManufacturerModelMaterialCapacityFill PressureLength (inches)Diameter (inches)Weight (Lbs)Buoyancy Full (lbs)Buoyancy Empty (lbs)
CatalinaS4Aluminum430007.83.211.9-1.6-1.4
CatalinaS6Aluminum6300010.83.212.6-1.2-1.2
CatalinaS13Aluminum13300012.84.385.7-1.8-0.9
CatalinaS19Aluminum19300017.74.387.8-1.5-0.2
CatalinaS20Aluminum20300013.85.259.2-1.40
CatalinaS30Aluminum30300019.95.2513.6-2.4-0.2
CatalinaS40Aluminum40300025.45.2516.2-1.51.4
CatalinaS45Aluminum45300017.76.8920.3-2.80.5
CatalinaS50Aluminum50300019.46.8921.8-2.41.2
CatalinaS53Aluminum53300019.27.2525.1-3.80.1
CatalinaC60Aluminum60330019.97.2527.3-5.6-1.2
CatalinaS63Aluminum63300021.77.2526.9-2.81.8
CatalinaS80Aluminum77.4300025.97.2531.3-1.64.1
CatalinaC80Aluminum77.4330025.57.2534.7-5.80
CatalinaC100Aluminum100330026.5842-5.22.2
FaberFX15DVSteel15344014.173.946.6-2.42-1.21
FaberFX23DVSteel23344219.53.948.6-2.64-0.66
FaberL27DVSteel27264014.435.4611.7-2.95-1.07
FaberFX40BKDVSteel40344217.77.2414.8-4.51-1.48
FaberL50SDVBSteel50264025.25.5118.9-2.431.24
FaberM71SDVBSteel71330020.476.8428.7-4.350.9
FaberFX80SDVBSteel80344220.877.2428.6-8.05-1.74
FaberHP80Steel 81.7344220.87.2528.3-8.05-1.74
FaberL85SDVBSteel85264025.987.0131.2-3.82.32
FaberL95SDVBSteel95264023.828.0237.2-5.371.69
FaberM100SDVBSteel100349824.217.2438.7-14.11-6.69
FaberFX100SDVBSteel100344225.397.2434.3-8.41-0.59
FaberHP100Steel 101.3344225.37.2524-8.41-0.59
FaberL108SDVBSteel108264026.778.0241-5.022.98
FaberFX117SDVBSteel117344224.218.0238.9-9.12-0.16
FaberHP117Steel 117.8344234.2837.6-9.120.35
FaberL120SDVBSteel120264029.338.0244.9-4.874.07
FaberFX120SDVBSteel120344229.337.2439.2-8.820.65
FaberHP120Steel 120.1344229.17.2539.2-8820.65
FaberHP133Steel 133344226.85842.4-9.081.45
FaberFX133SDVBSteel133344226.788.0242.7-9.081.45
FaberFX149SDVBSteel149344229.538.0246.9-9.412.35
LuxferS006Aluminum6.1300011.13.22.6-1.4-0.9
LuxferS13SAluminum13.2300013.14.46-1.8-0.8
LuxferS019Aluminum19.9300018.64.48-1.30.2
LuxferS030Aluminum30300019.35.312-1.30.9
LuxferS040Aluminum40300024.86.914.9-0.72.4
LuxferS050Aluminum48.43000197.321.3-2.51.1
LuxferS063Aluminum63300021.97.326.9-2.42.4
LuxferS072Aluminum69.63000266.928.5-1.43.8
LuxferS080Aluminum77.4300026.17.331.5-1.74.2
LuxferS80NAluminum77.4330025.87.335.4-30.1
LuxferS100Aluminum98.8330026.2841.1-4.62.8
LuxferS106WAluminum Hoop Wrap106435026.17.433.8-4.83.1
MetalImpactAL06Aluminum5.8300010.93.22.7-1.6-1.12
MetalImpactAL13Aluminum12.8300012.74.46-1.1-0.14
MetalImpactAL19Aluminum18.3300017.254.47.9-1.7-0.38
MetalImpactAL30Aluminum29.1300019.55.2512.3-1.60.68
MetalImpactAL40Aluminum38.8300024.95.2515.3-11.88
MetalImpactAL50Aluminum49.5300019.46.921.5-2.31.54
MetalImpactAL63Aluminum61300021.97.2527.2-2.32.38
MetalImpactAL72Aluminum703000266.927.8-0.94.38
MetalImpactALN80Aluminum76.2300025.47.2533.4-4.11.78
MetalImpactAL80Aluminum77.5300026.17.2531.9-1.54.26
MetalImpactAL100Aluminum98.2300026.25842-5.32.26
OMS / FaberC8Steel7.87264011.253.585-2.23-1.61
OMS / FaberC13Steel132640143.95.9-3.31-2.25
OMS / FaberC20Steel20264019.53.97.5-3-1.5
OMS / FaberC45Steel462640235.517.6-40
OMS / FaberC50Steel50264025.25.519.92-4.8-1.5
OMS / FaberC66Steel66264021725-5.151.67
OMS / FaberC85Steel85264026731-6.70
OMS / FaberC98Steel98264024838-7.730
OMS / FaberC108Steel112264026841-8-1
OMS / FaberC121Steel125264029845-9.50
OMS / FaberC135Steel131264030.7847-10.30.75
Pressed SteelLP-45Steel452640235.519.6-3.7-0.5
Pressed SteelE7-65Steel65344216.757.223.2-6.4-1.5
Pressed SteelMP-72Steel71.2330020.756.930-11.4-6
Pressed SteelE7-80Steel80344219.757.226-9.3-3.3
Pressed SteelLP-80Steel80.62640247.234.4-7-1
Pressed SteelE7-100Steel1003442247.232-8.8-1.3
Pressed SteelE8-119Steel119344224839.3-12.2-3.3
Pressed SteelE7-120Steel1203442287.236.6-10.3-1.3
Pressed SteelE8-130Steel130344225.56842.2-14.6-4.8
Pressed SteelE8-149Steel149344229.37847.5-12.8-1.7
WorthingtonLP27Steel27264014.55.511.9-3-1
WorthingtonX7-65Steel66.4344216.77.2525.1-8.7-3.9
WorthingtonLP77Steel77264023.27.2532.5-6.8-1
WorthingtonX7-80Steel81344219.87.2529.9-9-3
WorthingtonLP85Steel82.9264024.77.2536.8-7.1-0.7
WorthingtonLP95Steel93.3264023.7836.8-7.1-0.7
WorthingtonX7-100Steel99.5344222.77.2533.1-10-2.5
WorthingtonLP108Steel108.6264026.5845.95-10.7-2.6
WorthingtonLP121Steel120264029.2849.9-11.1-2
WorthingtonX7-120Steel120.6344227.77.2539.7-11-2
WorthingtonX8-119Steel123344223.9842.5-10.9-2
WorthingtonX8-130Steel131.4344225.3844.7-11.7-2

The buoyancy of the cylinders above are in salt water. Also, the weight and dimensions do not include the tank valves. 

If you are trying to determine which cylinder you are looking at, it may be helpful to look at our article on understanding tank markings. In it we go in depth into many of the engravings found on SCUBA cylinders. 

Also, if you are in the market for a new tank and want more help with choosing the tank that's right for you you may want to read our article on how to pick the perfect SCUBA tank for you

Also, For more information on specific cylinders we recommend you check with the cylinder manufacturers directly. The “additional resources” tab below contains links to the cylinder manufacturers listed above. You can find information that goes beyond the SCUBA tank size chart there. 

Additional Resources on SCUBA Cylinders

Choosing the best SCUBA Tank for you

How To Pick The Perfect SCUBA Tank That’s Right For You!

By Jose Cernuda

Choosing the best SCUBA Tank for you

Have you ever considered diving with a different size SCUBA tank than the one you normally dive with? Maybe you want to stay down longer so you figure a bigger tank will buy you some more bottom time? Perhaps the tank you always use just seems too big and bulky and you want a smaller, lighter tank that will be easier to handle? A bigger tank equals more gas. More gas may potentially get you more bottom time. How much more? Check out our nifty little calculator below (one of many throughout this article) to find out how much more or less gas you will have. 

  • Imperial

  • Metric

If you look at how much more gas you get by switching from an aluminum 80 (11 liter) to a steel 120 (15 liter) tank and what you want is more gas on your dives then you'd think the decision is a no-brainer. After all, you get 55% more breathing gas from making that switch. You can get even more out of even bigger tanks! However, there are other things to consider. Every SCUBA cylinder has its positives and negatives. You can see a full breakdown of the characteristics of different tanks in our chart of common diving tanks later in this article. 

There’s much more to choosing a SCUBA tank than simply getting a bigger or smaller tank for your needs. By reading this article you'll know more about SCUBA tanks than most divers do and how to choose the best one for you. 

What to consider when purchasing a SCUBA tank?

Many factors go into choosing the perfect  SCUBA diving tank for you. If you choose poorly you could end up with a tank you hate or one that simply sits around and gathers dust because you'll realize after a few dives that you'd rather not use it. . Some of the things you'll need to consider when choosing the tank that's right for you will include the size/capacity of the tank, the material (aluminum vs. steel), the physical weight of the tank, the buoyancy characteristics of the tank in the water, how the tank affects your trim, and, of course, the cost of the tank.

Tank Terminology - Getting To Know The Parts That Make Up Your Tank

Before you learn how to choose the right tank, you must understand the terminology used for tanks and what it all means so that you can fully understand the choices that you are going to make when choosing a cylinder.

Tanks, Botttles, Or Cylinders, What's The Difference?

Depending on where you took your SCUBA classes and maybe where your instructor is from, you may have heard either the term SCUBA tank, SCUBA cylinder or maybe even SCUBA bottle. They are all the same thing. In this article, we use the terms interchangeably. Just to be clear, if you hear someone mentioning any of the terms above, they are talking about the same thing.

Steel vs. Aluminum

All SCUBA diving tanks are made out of either aluminum or steel. Each material has pros and cons which we will explain later in this article. Generally speaking, steel cylinders tend to be more expensive, they also tend to hold more gas than a similarly sized aluminum tank. Steel tanks also generally tend to have better buoyancy characteristics in the water, but more on that later.

Pressure ratings

All SCUBA cylinders have a maximum pressure that they can be filled to. In the United States, we use pounds per square inch (PSI) to measure the maximum pressure. In many parts of the world, BAR is the unit of measurement used. One BAR is roughly equal to 14.5 PSI. 

Tanks come in three varieties when it comes to pressure.

Low pressure (2400 to 2540 PSI – 165 to 182 bar)

Standard (3000 PSI – 207 bar)

High Pressure (3300 to 3500 PSI -227 to 241 bar)

Again, each pressure has pros and cons which you will learn about in this article.

Capacity and Internal Volume

In the United States, all SCUBA tanks have a rated capacity. The capacity of a tank is the amount of gas a cylinder will hold when is full. In the Imperial system we use cubic feet to measure the capacity of a tank. The capacity of a tank is how many cubic feet of gas is inside the tank when filled to its rated pressure. So, as an example, an aluminum 100 cubic foot tank that is rated to 3300 PSI will hold 100 cubic feet of gas when the pressure inside is at 3300 PSI.

In other parts of the world capacity for tanks is expressed as its internal volume. The internal volume is expressed as the amount of water a tank can hold. This is mainly used in countries that use the metric system. So, a 9 liter tank holds 9 liters of water if it were filled with fluid. To determine the amount of gas a tank can hold you simply multiply the size of the tank in liters by its service pressure. So, as an example, an 9-liter tank that is filled to 207 bar will hold 1863 liters of gas when full (9 x 207 =1863). 

To get a better understanding of how pressure relates to volume when it comes to SCUBA cylinders check out our SCUBA tank volume calculator below. Notice on the calculator how, when the tank is full, you have the full capacity of the tank. As you move the slider to the left, the pressure decreases as does the amount of available breathing gas. 

SCUBA Tank Volume Calculator

  • Imperial

  • Metric

The K-Valve

Close up of a K-valve on a tank

SCUBA tanks can be purchased with or without the tank valve. If you are purchasing a SCUBA tank with a tank valve you'll most likely be purchasing it with a K-Valve. Most all modern SCUBA cylinders use a K-valve. There are other types of valves, but their use is a topic for another article. Just know that if someone refers to the K-valve they are talking about the SCUBA tank valve.

DIN vs. Yoke

When you choose a SCUBA tank often the tank will come with a K-valve. That valve comes in two varieties, a DIN fitting or a yoke fitting. Your choice is often determined by the type of regulator that you are using. Yoke fittings are for the clamp-on type of regulator and DIN fittings are for the screw-on type. You can tell the difference because the DIN valves have a larger opening and threading on the inside in order to screw on a DIN regulator. 

Notice how the DIN valve on the left has a large threaded opening for a DIN regulator to screw into. The Yoke on the right does not as yoke regulators are clamped on.

Burst Disk

The bolt in the center is the burst disk. It can be unscrewed and easily replaced.

The burst disc is a valve that screws into the K-Valve itself. It looks similar to a bolt and is there for safety. If a tank is filled to an unsafe pressure above the tank's maximum rated fill pressure, the burst disk will break and safely expel all the gas contained in the cylinder. The purpose is to have the burst disc break before the tank explodes.

Burst discs can rupture due to age or even temperature changes when the burst disk is faulty. When a burst disc breaks, it is LOUD! All of the gas will escape the tank in a matter of minutes. It can be pretty scary if one goes unexpectedly.

Gas Mixtures

Because SCUBA tanks can hold air, nitrox, trimix, argon or, even pure oxygen when used for decompression in technical diving, it’s common for divers to refer to what’s inside as gas. Saying a cylinder is filled with something like air or oxygen is usually only done so when you know what the content of the gas inside the tank is, and you are referring to it specifically.

Inspections

SCUBA diving tanks must be inspected periodically to ensure that the metal is structurally sound and can be filled safely by a SCUBA compressor. Because SCUBA cylinders contain pressurized gas inside, if the integrity of the metal were compromised, the tank can explode when being filled.

In the United States tanks are visually inspected yearly and hydrostatically inspected once every five years. After the visual inspection is passed, the tank is usually marked with a sticker indicating when the visual inspection was performed. When Hydrostatic inspections are passed the tank, is physically engraved with the date of the hydrostatic test. The hydrostatic test is frequently abbreviated to just hydro. It's common to refer to this exam as the hydro test or the hydro date. .

Tank Engravings

All tanks have markings engraved on the shoulder of the cylinder. These markings indicate things like the manufacturer, material of the tank (aluminum or steel), serial number, working pressure, and the original hydrostatic test. For more information on how to interpret these markings check out this article


Tank Labels

Other than the visual inspection sticker, it’s common practice to label tanks that are designated for use with Nitrox or other gasses such as Trimix. It’s also a common practice in the technical diving community to place labels on tanks indicating the mixture of gas that’s inside and its maximum operating depth.

Tank Coatings

In the presence of moisture, aluminum will oxidize and steel will form rust.

For this reason, steel tanks have a zinc coating. Depending on the manufacturer, the coating may either be a zinc dipped coating that is applied during the galvanization process of the tank, or a hot zinc spray coating that is then protected by epoxy paint. This is done to protect the tank from rust.

Aluminum cylinders are either painted, left natural, shot blasted, or brushed. Many people believe aluminum tanks are best left unpainted because once the paint begins to chip, moisture can get under the paint and oxidize faster than if no paint had ever been applied in the first place. Also, because chipped paint can end up in the ocean, many manufacturers have moved towards using paints that are more environmentally friendly. Many believe these paints do not adhere as well as the paints used on tanks of yesteryear.

Whether or not the paint helps the exterior of aluminum tanks to avoid rusting is a topic for debate. My personal preference for aluminum cylinders is no paint at all since, sooner or later, the paint will chip and scratch no matter what.

Tank Boots

Both Aluminum and Steel SCUBA tanks can have tank boots. A tank boot is a rubber or plastic sleeve that goes around the bottom of the tank. The boot's purpose is to protect the surfaces that the tank is placed on.

Because a tank is a heavy piece of metal, a tank without a boot can damage floors, the fiberglass on a boat, and even the cement inside of a swimming pool. Also, because the bottom of most steel cylinders are curved, tank boots make it so that you can stand up the tank. Notice how the steel cylinder in the image is curved. If it were not for the tank boot, you would not be able to stand this tank up. 

The drawback of tank books is that they can accumulate water and accelerate the oxidation process. For this reason, many divers choose to not have boots on their tanks.

Steel Vs. Aluminum

Now that you understand the tank terminology you can begin to figure out what tank(s) will be best for you. One of the first things you need to consider is whether to get a Steel SCUBA tank or an Aluminum SCUBA tank. Each has its pros and cons.

Aluminum Tanks

Most people begin diving with an aluminum tank. The most common tank is the aluminum 80 (11 liter) cylinder. Many dive boat operators and dive shops use this tank because 80 cubic feet of gas is enough to do most recreational dives safely, this cylinder is widely available and it’s also one of the cheapest tanks you can buy.

As a side note, the aluminum 80 does not actually contain 80 cubic feet of gas. Technically it contains 77.4 cubic feet of gas when filled to 3000 PSI. The number is rounded up to 80 by almost everyone. Two of the most popular manufacturers of these tanks are Luxfer and Catalina.

Just because you began diving with an aluminum cylinder does not mean that it is the best option for you. The main positive of using aluminum tanks is that they are cheaper and lighter than steel tanks.

For some specialized types of diving such as sidemount and technical diving, this is often the preferred option, but that is beyond the scope of this article.

Because aluminum is less dense than steel, many aluminum tanks will float when they are empty. You have to remember that the gas in the tank also has weight to it. As you consume the gas the tank will become lighter throughout the dive. All tanks will become lighter throughout the dive as you consume the gas contained inside. In the case of aluminum tanks, the shift in buoyancy from the start of the dive to the end of the dive is enough that most divers need to add weight to their BCD or weight belt to offset the positive buoyancy.

The slider below illustrates how an aluminum 80 goes from being negatively buoyant when full to being positively buoyant when empty. The concept is the same in the metric system even though the units of measurement are different. 

Keep in mind that many divers need ballast to be able to descend in salt water. If a diver were to rely on the negative buoyancy provided by the gas inside a tank at the start of a dive, at some point during the dive, as the gas is consumed, the diver may become too positively buoyant to be able to stay underwater. This can be a dangerous situation. You can see in the video below how the same aluminum cylinder will have completely different buoyancy characteristics depending on the amount of gas that's inside. 

Something else to consider about aluminum tanks is that they hold less gas than a similarly sized steel cylinder.

Finally, because aluminum is a weaker material than steel, many dive shops will not fill older aluminum tanks.

The good thing about aluminum tanks is that they are cheaper and lighter on the surface than steel tanks. 

Pros: Familiarity, Cheap, lighter to carry around on the surface

Cons: Unfavorable buoyancy characteristics, you need to add ballast to offset its buoyancy, they hold less gas than steel cylinders and tend to have a shorter lifespan.

Steel SCUBA Tanks

Many experienced SCUBA divers as well as technical divers prefer steel cylinders. The main reason is that they hold more gas than a comparably sized aluminum tank and they also usually have more favorable buoyancy characteristics.

Because steel is a denser material than aluminum, steel SCUBA tanks tend to remain negative even when they are empty. This means you can use less ballast on your SCUBA rig. Also, because the weight that you take off of your rig is being distributed across your back, you will usually trim out better in the water than you would with a comparable aluminum cylinder (more on this later).

Also, steel tanks are available in larger capacities than aluminum tanks. If you need more than 100 cubic feet of gas in a single cylinder, then steel is the only choice.

As mentioned previously, steel SCUBA tanks also tend to have a longer lifespan than aluminum tanks. For this reason, many divers believe that, when you look at the true cost of owning steel, it isn’t more expensive when you consider the longer life.

The downside to steel SCUBA tanks is that they are more expensive to purchase. Also, you need to be careful to make sure you rinse off your tanks if diving in saltwater and pay attention to any water that may collect in the tank boot if you have one. This can lead to corrosion over time. You also should, as with all cylinders, never drain them completely to avoid the possibility of moisture entering the tank. Finally, steel cylinders tend to be heavier out of the water than aluminum cylinders. 

Pros: Hold more gas than a comparable aluminum tank, better buoyancy characteristics, better trim properties, only choice for larger capacities

Cons: More expensive, can corrode if not maintained, heavier to carry around on the surface

Chart of common SCUBA cylinders

Below is a chart of some of the common SCUBA cylinders used by divers. This list is not comprehensive. However, if you compare the cylinders you should begin to get an idea of how different tanks have different buoyancy characteristics. For a more comprehensive list, check out our article dedicated to tank specifications

  • Imperial

  • Metric

ManufacturerModelMetalVolumeFill PressureLength (inch)Diameter (inch)Weight (lbs)Buoyancy Full (lbs)Buoyancy Empty (lbs)
CatalinaC60Alumium60330019.97.2527.3-5.6-1.2
CatalinaS63Alumium63300021.77.2526.9-2.81.8
CatalinaS80Alumium77.4300025.97.2531.3-1.64.1
CatalinaC80Alumium77.4330025.57.2534.7-5.80
CatalinaC100Alumium100330026.5842-5.22.2
FaberM71SDVBSteel71330020.476.8428.7-4.350.9
FaberFX80SDVBSteel80344220.877.2428.6-8.05-1.74
FaberL85SDVBSteel85264025.987.0131.2-3.82.32
FaberL95SDVBSteel95264023.828.0237.2-5.371.69
FaberM100SDVBSteel100349824.217.2438.7-14.11-6.69
FaberFX100SDVBSteel100344225.397.2434.3-8.41-0.59
FaberL108SDVBSteel108264026.778.0241-5.022.98
FaberFX117SDVBSteel117344224.218.0238.9-9.12-0.16
FaberL120SDVBSteel120264029.338.0244.9-4.874.07
FaberFX120SDVBSteel120344229.337.2439.2-8.820.65
FaberFX133SDVBSteel133344226.788.0242.7-9.081.45
FaberFX149SDVBSteel149344229.538.0246.9-9.412.35
LuxferS063Alumium63300021.97.326.9-2.42.4
LuxferS080Alumium77.4300026.17.331.5-1.74.2
LuxferS80NAlumium77.4330025.87.335.4-30.1
LuxferS100Alumium98.8330026.2841.1-4.62.8

High-Pressure Vs. Low-Pressure

As you look at the chart above you should notice that different tanks have different service pressures. The service pressure is the maximum pressure a tank can be filled to. The capacity of the tank is measured at its service pressure in the imperial system. In the metric system you multiply the capacity of the cylinder by its fill pressure in bar. 

Below are the definitions for low, standard, and high-pressure:

Low-pressure (2400 to 2540 PSI – 165 to 182 bar)

Standard (3000 PSI – 207 bar)

High-Pressure (3300 to 3500 PSI -227 to 241 bar)

This brings up the question, is there any advantage to low pressure vs. high-pressure tanks?

In general, high-pressure tanks put more stress on O-rings and the internals of your SCUBA regulator. With modern regulators and if you are regularly servicing your equipment as recommended, this should not be a problem.

The only disadvantage high-pressure tanks may happen if you are filling your tanks with Nitrox from a provider that uses a partial pressure filling system and does not have a gas booster. If they are using this system and they are running low on oxygen, they may not be able to get the oxygen level high enough in your tank for you to reach your desired mix.

This can also happen with standard pressure and low-pressure tanks it’s just that because you need to reach a higher pressure with the high-pressure tanks, they are the most affected.

Another disadvantage of high-pressure tanks is that, if the dive shop you go to does not regularly fill high-pressure tanks, they may mistakenly under-fill your tank. This is easily remedied by checking your tanks before you leave the shop.

The big advantage of course is that you get more gas with high-pressure tanks.

Some people prefer low-pressure tanks because they are not as negatively buoyant as high-pressure tanks.  Here, your gear configuration and your buoyancy requirements will come into play. Another reason for choosing low pressure tanks for some, is because they place less stress on your regulator. 

One thing to be aware of if purchasing a low-pressure tank is the plus rating. When many low-pressure tanks are first sold, they are technically rated to 2400 PSI. The original hydrostatic test then has a plus rating that allows them to be over-filled by 10 percent. This plus rating is indicated by a “+” after the original hydrostatic date. This additional 10 percent brings the working pressure to 2640 PSI. When they are sold, they are marketed at the capacity reached at 2640 PSI (with the plus rating).

The image to the right shows the original hydrostatic exam performed on a steel cylinder. This hydro exam was performed on January of 2003. This is indicated by the 01 and the 03 respectively. The "+" sign after the date lets the person filling the tank know that this cylinder can be overfilled by 10 percent. 

Sometimes when you have the hydrostatic testing done on the tank years later the operator will not conduct the test for the plus rating. If the subsequent hydrostatic test does not have this plus rating, then the tank may not get filled to its original capacity by some dive shops.

DIN Vs. Yoke

When purchasing a SCUBA cylinder, you’ll often have a choice as to the type of fitting you want for your K valve. The choice will most likely be determined by the type of regulator that you own. 

As mentioned previously, the K-valve that comes on a SCUBA cylinder can be either a DIN or Yoke fitting. You can see in the image below the difference in how yoke regulators are clamped on and DIN regulators are screwed on. 

The Yoke Valve

The Yoke Valve is a clamp-on type of valve. It is the earliest type of valve used by the original Aqua Lung SCUBA regulators. The yoke style regulator is also sometimes called an A-Clamp. The only real advantage to this type of valve is that clamping on your regulator is slightly faster and easier than screwing it on. It’s not a big deal however, we’re only talking about a few seconds difference when setting up your rig.

SCUBA DIN Valve

The DIN valve is a screw-on type of valve. They are a newer type of fitting and are gaining popularity over time. The DIN fitting is more secure which means it is less likely to leak. Also, because there isn’t a clamp sticking out of the back it’s less likely to get knocked loose during the dive. DIN valves are preferred for this reason by technical divers.

DIN Valves come in 2 varieties: 200 BAR and 300 BAR. The difference is that the threading on the 300 bar valves are a bit deeper to accommodate more threading and hence higher pressures. You can fit a DIN regulator made for 300 BAR into a 200 bar valve without issue. You can see in the image below how the same regulator fits more snugly on the 300 bar valve but has some threading exposed when placed on a 200 bar valve. 


If you have the choice as to what kind of valve to get with your SCUBA TANK our recommendation is to get a 200 bar DIN valve with a donut insert. This is sometimes referred to as a convertible DIN valve. You can see an image of one below. 

The donut insert adapter converts a 200 bar DIN valve into a yoke valve. This way you can have the flexibility of using either regulator. This is always convenient if you need to lend your tanks to a dive buddy who doesn’t have the same type of regulator set up that you do.

Choosing a Tank Capacity

Now that you know about all the parts of a tank, the materials it is made of, and the types of valves you can get with one, it’s time to begin to figure out what the best tank size is for you.

The capacity of the cylinder you choose is determined by your breathing rate, the depth you plan to dive to, and how long you plan to dive to a particular depth. You also need to factor in the amount of gas you’d like to have in reserve in addition to the gas you’ll consume throughout the dive.

Your Surface Air Consumption (SAC) Rate or Respiratory Minute Volume (RMV)

The most precise way for you to figure out how much gas you will consume is by knowing your Surface Air Consumption (SAC) rate or Respiratory Minute Volume (RMV). Both measurements are used to measure the rate at which you consume the gas inside your tank.  We wrote an in depth article explaining the difference between the two here. The main difference between the two measurements is that SAC measures your breathing rate in PSI per minute (BAR per minute), and RMV measures your breathing rate in cubic feet per minute (liters per minute). Your SAC rate is tied to the tank you measured your breathing rate on. For this reason, we prefer to measure breathing rate in RMV. Most people in the dive industry use both terms interchangeably. 

Your RMV rate is the amount of gas you consume per minute while diving. The number is expressed at the surface. So, as an example, a diver with an RMV rate of 1 Cubic foot per minute can expect to consume 2 cubic feet per minute at 33 feet, 3 cubic feet at 66 feet, and so on…

If you know this number, you can use it to estimate how much gas you will need for any given dive. 

Planned Depth

To determine the correct tank size, you need to know what depth you plan to dive to. The deeper you go the faster you will consume your gas due to the increase in atmospheric pressure. This is why it is common for experienced divers to use bigger tanks for deeper dives.

Time at Depth

More time underwater equals more gas consumed. This is especially true on deep dives.

If you are at 99 feet (10 meters) for example, you can expect to be breathing 4 times the amount of gas that you would be at the surface with each breath because of the increased atmospheric pressure.

One way to plan for time at depth in recreational diving is by looking up the no-decompression limits at the depth you plan to dive to on a decompression table. You can then use the maximum time allowed at the given depth. This does NOT mean you should dive to the absolute limit, it’s just a way of estimating the amount of gas you might need conservatively.

Because most dives end up being multi-level dives another way to estimate the gas you’ll need on your dives would be to use your dive data from a dive computer and estimate how long you tend to dive at a particular depth.

Either way, it’s best to over-estimate the amount of gas that you will need since having more gas than what you need will only make your diving safer.

Gas Needed For A Dive Calculator

  • Imperial

  • Metric

Reserve Gas

Once you know the gas you will need at depth, you should add in additional gas as a reserve. We all learned in our entry-level SCUBA course that you never dive until a tank is empty. It’s common for dive operators to tell divers they should be back on the boat with no less than 500 PSI or 35 Bar. This is usually assuming an 80 cubic foot (11 liter) tank. As stated earlier, it’s best to over-estimate the gas you’ll need. It’s also a good idea to try to have more reserves than the minimum.

Estimating Gas Without Your SAC or RMV Rate

If you do not know your SAC or RMV rate, a less precise way to estimate your gas requirements would be to look back at your dive log and estimate the amount of gas you would need to complete the type of dive you want to do.

Let's say as an example that you have done a dozen or so dives to a shipwreck at 100 feet (30.5 meters) using Nitrox and an aluminum 80. Your average dive was around 24 minutes returning to the boat with 500 PSI (35 BAR). You would like to have more bottom time, so you know you will need a bigger tank.

Following our example, the NDL at 100 feet (30.5 meters) for 32% Nitrox is 30 minutes (this number varies depending on which table you look at). This means you’d like to get 6 additional minutes or 25 percent more time. So, you’ll need a tank that has at least 100 cubic feet of gas to accomplish this.

Round-Up the Estimated Amount of Gas

It’s important to realize that you’re better off having more gas than what you need for a dive than not having enough. For this reason, when in doubt about choosing two similar tanks you’ll usually be better off choosing the larger size.

Tank Buoyancy, Trim & Size Characteristics

Tank Buoyancy

Once you know how much gas you need to be able to do your desired dives, you need to consider the buoyancy characteristics of the tanks that hold the amount of gas that you need. Different tanks have different buoyancy characteristics.

In the video below you can see how I was able to add just enough weight to an aluminum 80 to get it to be neutrally buoyant in fresh water. This is an exercise I suggest you do for yourself with the tank that you dive. You want to know exactly how much weight (if any) you might need to offset the buoyancy of your tank at the end of the dive. Do not rely on manufacturer specifications or SCUBA charts! We've found that those numbers can be off in the real world when testing for ourselves. 

Note that the buoyancy characteristics of tanks on most graphs are usually for saltwater diving. Fresh Water will affect your buoyancy and the buoyancy of the tank you use. You'll need less lead in fresh water than you would in saltwater. Tables, like the one on this page should only be used to compare similar tanks and get an idea of the cylinder you want to use or purchase. You should perform your own buoyancy check for your tank as shown in the video above. 

If you’ve done a proper buoyancy check and know how much lead you need to be properly weighted then you might want to consider using a steel tank to offset some of the ballast that you’re using either in your weight belt, integrated weights, or even in the form of a stainless steel backplate. Doing so has three advantages. First, by spreading the weight across your back you'll trim out better (in a more horizontal position) in the water. Second, by shedding some of the ballast you need to dive, it'll be easier to carry your dive gear. Finally, if you move to a steel tank you'll usually be able to get a tank with a higher capacity (more gas) in a similar size as an aluminum tank. 

Something else to consider is if you know you need little to no weight, or if you are diving in freshwater, then you may need to consider the amount of lift your BCD or Wing provides and whether it’s enough to offset the negative buoyancy of the tank that you are considering.

Similarly, if you are using a thick wetsuit or a drysuit when you go diving then you need to consider the buoyancy characteristics of the suit and undergarments you are using. Here it may be advantageous to choose a cylinder that's more on the negative side to help offset the positive buoyancy created by your suit. 

Proper weighting is a completely different topic. For more information, you may want to see this in article.

Tank trim Considerations

Something else to consider when choosing your tank is how it will affect the way your body trims out in the water.

Consider the diagram below. The diver on the left is using aluminum 80 (11 liter) tank while the tank is still full and negative. Notice where their center of gravity is. The diver on the right is using a high pressure steel 80 (10 liter) tank. Both tanks hold the same amount of gas when full. Notice however, that because the high pressure steel tank on the right is shorter, the center of gravity shifts. It helps the diver maintain a more horizontal and streamlined position during the dive. This does not mean that choosing the right tank is the only way to properly trim out a diver but it is a factor to consider. 

Tank Size Considerations

How large or small a Cylinder is will affect how easy it is to carry and store your tank. A high-pressure steel 133 cubic foot tank for example, is both larger heavier, and bulkier than a Aluminum 80. The 133 cubic foot tank will however give you 55 additional cubic feet of gas during your dive. You can see the size difference in the image to the left. 

If you are considering getting two different tanks that each have a different diameter you should know that you will have to adjust the tank strap on your BCD when you switch from one tank to the other. It’s not a big deal, but it is a small inconvenience you should be aware of. You can see that difference in diameter in the picture above. 

Hidden Tank Costs

Overall if you dive enough it’s usually more economical to own your tanks. It’s also best because you can have the tank size and weight that best suites you.

You should, however, be aware of the costs associated with owning a tank. Over the life of the cylinder, you’ll have to pay for more than just the gas fills.

Visual & Hydrostatic Inspections

Every country has regulations regarding how compressed cylinders need to be maintained. In the United States, the Department of Transportation (DOT) regulates SCUBA cylinders. In the US, SCUBA cylinders need to be visually inspected yearly, and hydrostatically inspected every 5 years. This is a cost you should factor into owning a tank. Prices for this varies, so check with your local dive shop.

The visual inspection is performed by dropping a special light into the tank to check for any signs of corrosion, cracking, pitting or anything else that may affect the structural integrity of the cylinder.

Some service technicians may also perform a visual eddy as part of the visual inspection. This is an additional test where an electrical current is run through the neck of the tank in order to further check the structural integrity of the tank.

When a visual exam is passed a sticker is placed on the tank to indicate the date when the visual inspection was performed and passed. You can see an example of a visual inspection sticker from a local dive shop in the photo to the right. 

A hydrostatic exam requires a special machine. There are several ways to perform this test. The most common is a machine where the tank is placed into a steel container that is surrounded by water. The machine then pressurizes the SCUBA cylinder to five thirds of its working pressure. The technician will measure the expansion of the metal under pressure. If the tank is within the allowed tolerances for the exam, it will pass the test.

When a hydrostatic test is passed the tank is permanently engraved with the date of the hydrostatic test.

Both the visual and hydrostatic tests are essential to make sure SCUBA cylinders are safe to fill. Dive operations can deny filling any SCUBA cylinder they feel may be unsafe to fill. This is because, if a SCUBA cylinder bursts while being filled, it’s like a bomb exploding. It can kill or injure anyone who is unfortunate enough to be nearby as well as cause significant property damage.

Valve maintenance

Over time the O-rings and other internal parts of a SCUBA valve can become worn and even corrode. Your local dive shop will inspect the valves at a minimum when you do the visual inspection. From time to time, the valves will need to be rebuilt since, just like your regulator, they are mechanical and need to handle 3000 PSI (207 BAR) or more regularly.

Tank & Valve Cleaning for Nitrox

If your SCUBA tank will be filled with Nitrox, you’ll most likely need to have the tank and valve cleaned for Nitrox. Most SCUBA cylinders come cleaned for Nitrox from the factory, but once the first hydrostatic test is done, you’ll need to clean the tank afterward.

Additionally, many dive shops will require you to label your tank with a “Nitrox” sticker. This is so that everyone knows that the tank contains a mixed gas and to avoid anyone confusing your tank for an air tank.

Renting Vs. Buying

When to Rent

Should you even buy a tank at all? If you have to fly to get to all of your diving destinations, then owning a tank doesn’t make sense. Also, if you live far enough from a dive shop that driving there to fill your tanks is a major inconvenience, then you’ll probably also be better off renting your tanks when you dive.

Another thing to consider is how often you dive. If you only dive several times a year all the hassle of filling and maintaining the tank may not be worth it to you.

When to Buy

If you dive fairly regularly and live close enough to a dive shop that can fill your tanks, you’ll probably want to own your tank.

Below are just some of the advantages of owning your tanks:

  • You can match the size of the tank to the gas that you need for a dive
  • You can choose a tank that has better buoyancy characteristics
  • Your tank can help you achieve better trim in the water
  • You can have more control over the mix of gas inside the tank and not be limited to what may be available for rent
  • You can choose the type of tank valve that you prefer

What to Do If You Can't Buy

If buying a tank doesn't make sense because you travel to dive or it's simply inconvenient, it doesn't necessarily mean you need to settle for whatever the dive operator gives you. Many dive operators rent out different size tanks and steel tanks as well as aluminum ones. If you want to dive something other than the standard aluminum 80 (11 liter) you should ask. If the operator you ask doesn't carry a variety of different tanks then you might want to ask a different dive operation that goes to the same sites. It might be as simple as making a phone call or browsing their web site. 

How Many Tanks Do You Need?

How many tanks you’ll need will depend a lot on how often you dive, what types of dives you do, and what you can afford.

If most of your diving is going to be using commercial dive operators, you’ll probably want to start with 2 tanks since most dive trips consist of 2 separate dives.

Your first 2 tanks should be able to hold enough gas for the deepest dives you plan on doing. Since you’ll only have 2 tanks, you’ll want to be able to do both deep and shallow dives. It’s better to have bigger tanks that you can also use on shallow dives than to get tanks that are too small for you to use on deeper dives.

If you do a lot of diving in both shallow water and deep water, you may want to consider owning 4 tanks. One set of tanks for the shallow dives and another for deeper dives. This is a personal choice if you want to go this route. The advantage of having smaller tanks for shallow dives is that they are easier to handle and may trim you out better in the water.

For most recreational divers 4 tanks are more than enough to cover just about anything they might want to do.

Tank Maintenance

A SCUBA diving tank is a long-term investment. Regardless of which cylinder you decide is best for you, you’ll want to take care of it so that it can last as long as possible. Below are some suggestions to help get the most life out of your SCUBA tank.

Rinse after every use

If you are diving in salt water, you’ll want to rinse the tank off after every use. Saltwater left on tanks can accelerate the oxidation process. Don’t forget to rinse off the tank valve thoroughly since it contains moving parts.

Never completely drain your tank

The inside of your SCUBA diving tank is particularly vulnerable to oxidization if moisture gets in. Luckily the easy way to avoid this is to never completely drain your SCUBA tank.

Even if you never completely breathe down your tank during the dive it’s still possible for the tank to drain after the dive. A small regulator leak or even a low-pressure inflator that’s leaking ever so slightly can slowly drain the tank if it’s not disconnected or at least turned off. So, make sure you close your SCUBA tank valve after the dive is complete.

Periodically remove your boots

As mentioned earlier tank boots tend to collect water inside of them. If you choose to have boots on your tank, consider removing them when you are rinsing your tank and allowing the tanks to dry without them. If this is too much of a hassle to do every time at least check periodically to ensure there is no oxidation forming under the boots. Better to catch it early and fix it than to allow the oxidation to grow.

If the valve got wet, open and close it before connecting a regulator to it

This one isn’t strictly for your SCUBA tank, but it’s worth mentioning. If your tank gets wet because of rain, because it was dunked in a rinse bucket, or any other reason, you want to make sure the moisture that may be in the valve doesn’t get into your regulator and damage it. A quick opening and closing of the valve should shoot any moisture that’s trapped inside the valve out so that it doesn’t escape under pressure into your regulator’s first stage.

Don’t forget your visual and hydrostatic inspections

Dive shops won’t fill your tanks if they are not current on their inspections. There’s nothing worse than going in to get your tank filled a few days before a planned dive only to realize you can’t get your fill because it’s due for a hydro. It’s a good idea to set a calendar reminder for when your visual and hydros are due so you don’t get caught by surprise

If you suspect water entered a tank, take it to your dive shop as soon as possible

As mentioned before, moisture inside a SCUBA diving tank can ruin the tank. Your dive shop can inspect the inside of your cylinder to see if any damage was caused by moisture inside the tank. If there is oxidation there is a process called tumbling which can be performed to remove the oxidation and restore the tanks for continued service.

If a Cylinder is involved in a fire, a significant car accident, or anything else that may affect its material strength, have it tested

It’s always better to be safe than sorry. All of the above can weaken the material of a SCUBA tank. If your tank was involved in a house fire or anything that may weaken it, then you should let your local dive shop know and have the tank tested before having it filled. Anything that affects the structural integrity of the tank's metal can be extremely dangerous if the tank explodes while it is being filled. 

Tank Under-fills - Why doesn’t my dive shop fill my tank to its service pressure?

One of the complaints many divers have is that when they check their tank at the dive site it isn’t full. Below are several reasons why this may happen.

Hot Fills

When SCUBA tanks are filled with compressed gas they tend to heat up. Ideally SCUBA tanks should be filled slowly to avoid tanks getting too hot. However, no matter how slowly they’re filled, SCUBA tanks will usually heat up somewhat while being filled. This heat causes the molecules of gas inside the tank to expand somewhat producing a higher pressure. Once the tank cools down, the pressure drops a bit and can cause you to have a fill that is less than the pressure that was read when it was hot.

The best way to avoid this is to drop your tanks off with plenty of time so that your tanks can be filled properly and so that they can cool off. Then make sure you check your tanks before leaving. If they are under the rated service pressure, you can always ask to have your tank topped off.

Cold Temperature Outside

Just as hot air expands cold air will contract. A tank that was filled at service pressure in a warm environment can appear to have less gas when taken outside if it’s cold. This is also common if you are diving in cold water. It’s something to keep in mind when selecting your SCUBA tank. If you frequently dive in cold water you should account for the fact that your tank will most likely be under its full service pressure when you enter the water because of the cold environment. 

The compressor operator is unfamiliar with your SCUBA tank

From time to time you may have a situation where the person filling the SCUBA tanks incorrectly assumed the service pressure of your tank. They may be used to filling all tanks to 3000 PSI and your tank has a service pressure of 3300. Maybe they saw that your tank was a low-pressure tank but missed the “+” rating on it and only filled it to 2400 PSI instead of 2640. Whatever the reason, this is why you should always check the pressure in your tanks before leaving the dive shop.

How to Store and Transport Tanks

Always lay your tank down

Because SCUBA tanks contain compressed gas, it’s always best to lay them on their sides to avoid a tank tipping over and possibly damaging the valve. It is possible that if a tank fell and damaged the valve on the way down that the damaged valve now leaking compressed gas could cause the tank to move violently and cause further damage or even injury.


Always leave some gas inside the tank

As mentioned previously, SCUBA tanks should never be completely drained. This is to avoid the possibility of moisture entering the tank. If SCUBA gear is attached to a SCUBA cylinder, make sure the valve is completely closed.

Always secure your SCUBA tanks when transporting them

You should never allow tanks to roll around in the trunk of a car or the bed of a truck. An unsecured tank’s valve can easily get hit and begin to drain. There’s nothing worse than coming to a stop in your car hearing the tanks in your trunk shift around and then suddenly hearing the hissing of gas leaving your filled SCUBA tank.

Securing your tanks can be accomplished by using a ratchet tie-down, using a portable cylinder rack (usually made out of foam or PVC), or simply wedging the tanks with your dive bag or other gear.


Conclusion

There are a lot of factors that go into choosing the tank that’s right for you. Some of the factors that you need to consider when choosing a tank are the amount of gas you’ll need for the dives you’ll be doing, the buoyancy characteristics of the tank you choose, and how the tank will trim you out in the water. Additionally, you should also consider the type of SCUBA tank valve you’ll need, whether or not to dedicate the tank for Nitrox use, and of course price. Choosing the right SCUBA cylinder can help you have longer more enjoyable dives. It’s one of the pieces of dive gear that most influences your diving. 

What SCUBA tank do you dive with? Are you looking to change to a bigger or smaller tank? If so, why? Let us know in the comments below. 

Additional Resources on SCUBA Tanks

Warning: Why Your Weighting May Be All Wrong and How to Fix It

By Carlos Sagaro

If you’re like most divers, you probably have a set amount of weight that you carry with you as ballast when you dive

What you may not realize is that how you carry that weight is almost as important as the amount of weight itself.

Have you distributed that weight evenly across your rig so that your trim is balanced and you’re comfortable during your dive?

What would you do with the weight you carry with you in an emergency?

Is it important to you to be able to ditch your weight? If so, how much?

If you’re curious about the answers to any of these questions, then you’re going to want to read on.

In this article, we’re going to discuss a hot topic which is often overlooked yet critically important to your buoyancy control, trim, comfort and even your safety when you go diving.

One of the things that is counter intuitive when you learn to dive is the fact that you need to add weight to SCUBA dive.

Using an incorrect amount of weight when diving is one of the most common mistakes that many divers make. In many cases, people are diving with more weight than they need.

The cause may be doing an improper buoyancy check, sticking to weight that’s always been used but never tested, or simply adding more weight than what is really needed and compensating for it by adding air to the BCD.

Whatever the reason, in this article, we are going to dig into weighting and how you can use it to your advantage to improve your buoyancy, comfort level, breathing rate, and over all diving experience.

Why is Weighting Important?

Knowing and understanding how to be properly weighted will do wonders for you diving experience.

If you are over weighted or under weighted, your experience underwater is going to suffer. Let’s dig into some examples so you can see how:

What happens when you are over-weighted? 

First, imagine you were diving just 6lbs overweight. There are several problems which you will encounter. let’s go through them one at time.

  • Extra weight to carry around needlessly: That extra weight is going to need to be carried on and off of the boat. You may also be carrying it in your gear bag which is already heavy enough as is. What’s the point of carrying around dead weight that’s not needed?
  • Your propulsion may suffer: Every time you kick you’re moving more weight around than what is needed. It’s not just that weight itself. Because you need to compensate for the extra weight to stay neutrally buoyant you need to add extra air into your BCD. That extra air creates additional drag. This means more weight AND more drag in the water.
  • Your rig is likely off balance: It’s not just the amount of weight that you carry into the water, it’s where you position it that makes a difference in your diving. If like most divers you’re simply adding more weight to a weight belt or a BCD with ditch-able weights, there’s a good chance that, when you stop moving in the water column, your body is not in a balanced horizontal position like it should be.
  • It’s harder to get into and out of the water: That extra weight makes it harder to climb boat ladders. Even if you’re taking your rig or weight belt off and handing it up to climb on to a boat it’s still extra weight that doesn’t need to be there.
  • It can be extremely unsafe in the event of an emergency: If your BCD bladder or wing were to fail underwater this is now extra weight that you will need to swim up. If you ditch it, it may make it impossible to hold a safety stop or even lead to you having a fast or an uncontrolled ascent to the surface.

What if you were to be diving under-weighted? The circumstances are different, but just as serious.

What happens when you are under-weighted? 

  • Not being able to compensate for consumed gas: One of the reasons you may need to carry additional weight is to compensate for the shift in buoyancy which happens as you consume the gas in your tank. The video below explains this shift in gas that happens when you dive.
    • This is especially prevalent when you use aluminum tanks. As you consume the gas in your tank, it becomes lighter and lighter. Eventually the weight of the gas that was keeping your buoyancy negative is no longer there. It’s at this point that you find yourself having to fight to stay down.
  • Needing to change your body position to stay underwater: When you do not have enough ballast, you cannot hover effortlessly underwater. Because of this, you need to either kick or hold on to something to keep from floating up. Needless to say, if you are kicking to stay down you’re consuming the gas faster and the cycle becomes worse and worse as you have less gas and less gas in the tank.



Types of Dive Weights

Now that you understand why it’s incredibly important to be properly weighted, let’s start at the beginning. There are several types of weights used by divers and each one of them has its pros and cons. In this section we are going to discuss a few of those systems and their characteristics.

Solid Lead Weights

Every diver has come across solid lead weights at one point or another in their diving. These are a tried and true type of weighting system.

To be thorough, because the name itself implies what they are, solid lead weights are a piece of lead molded to fit a weight belt. They come in a variety of sizes ranging from .5lb to 10lbs (.23 kg to 4.5 kg). In some cases, they are incased in rubber to make them more comfortable around the body and to minimize lead exposure.

The biggest plus about these weights is that they are the most compact and therefore produce the least amount of drag. They are one of the least bulky of the options. They also tend to last forever. They can be used both on a belt or inside BCD pockets. (more on this later).

The biggest con is that they can be uncomfortable if they’re in a position on your weight belt where they are hitting your hip bone. Also, you must be careful to not drop them as doing so can be very painful and can even cause injury if they land on your foot.

Beaded Lead Weights

These are also extremely common. They range in sizes starting at .5lb to 10lbs (.23 kg to 4.5 kg). They consist of lead beads that are incased in mesh to allow them to dry and so that water will not accumulate inside of them.

There are several benefits to these types of weights. They are softer which makes them much more comfortable to store inside of BCD pockets and pocketed weight belts. Being malleable, they can counter to a diver’s body which makes them more comfortable when work on a weight belt. Lastly, and this has saved many a diver, if dropped they cause little to no damage.

As for the cons, beaded lead weights tend to be a bit more expensive. They also are bulkier, especially when used on a weight belt. Finally, the life span is probably not as long as lead weights since the material used to hold the pellets inside can rip.

Using Your SCUBA Tank as Ballast

It is common knowledge that tanks come both in aluminum and steel. While many divers do not think of them in this manner, steel tanks can be used as a weight.

Steel tanks as ballast

Unlike aluminum tanks, Steel tanks tend to remain negative even when they are empty. Additionally, Steel tanks are generally heavier than aluminum tanks and therefore can be used as a form of ballast. Steel tanks also tend to hold more gas than a similar size aluminum tank.

Finally, because the weight of a steel tank is distributed evenly across your back, steel tanks are often a good choice because they make it easier for you to achieve good trim and body positioning while on a dive.

The cons to diving steel tanks are that they tend to be more expensive, require more maintenance, and are usually heavier out of the water.

Aluminum Tank Considerations When It Comes To Weighting

Unlike most steel tanks, aluminum tanks tend to start negative and then end up slightly positive towards the end of your dive.

Just like steel tanks, when you are diving with aluminum you must consider where the tanks buoyancy characteristics end up at the end of your dive.

If you are neutral with a full aluminum tank at the start of you dive, you will be positive at the end of you dive which could cause all sort of problems. This means that you need to carry additional ballast to compensate for the positive buoyancy caused by a tank that is floating at the end of the dive.

Aluminum tanks are the most common type of tank because they are generally cheaper and also easier to maintain.

The bottom line is, whether you are diving with a steel or an aluminum tank, you must be aware of the tank’s buoyancy characteristics when it is empty or near empty. The last thing you want is to be slightly positive at the end of you dive.

Additional Tank Considerations

It is important to note that all tanks tend to become less negative as they start to empty during a dive. Every tank is different, and tank manufacturers publish charts which you can use to determine which tank is best for you.

Using these charts, you can get a good idea of what the buoyancy characteristics of different tanks are. However, you should be aware that these charts are only a starting point in helping you determine the amount of ballast that you’ll need.

Tank manufactures usually list the buoyancy characteristics of a tank without including the weight of the valve or the tank boot (if there is one). Additionally, the buoyancy characteristics are listed for a completely empty tank (something you should never do). Finally, you should also note if the buoyancy characteristics are for salt water or fresh water.

Armed with this knowledge and knowing the amount of gas that you will need for a dive, you can choose the most appropriate tank for your needs.

Regardless of whether you have a new tank or if you are using the same tank you’ve always used, you should always perform a buoyancy check with the tank being at its reserve pressure, either with your SCUBA gear on, or off the gear by itself in order to determine its buoyancy.

Common Types of Weighting Systems

Weight Belts

Weight belts are exactly what they sound like. A belt that you use to hold weights when you dive. There are two types of weight belts. The first is a basic nylon belt that you slide solid weights onto. The second is a pocketed that you can slip weights into.

The nylon belts can only hold solid weights. If you use this type of belt you’ll also want to use a belt slide or stopper to keep the solid weights in their place.

The pocketed belt can hold both solid weights and beaded weights. Whether you are diving with a nylon or pocketed belt, they both should have a quick release in the event of a diving emergency. (we will go into ditching weights later in this article.)

Integrated weight pockets on BCD

It is fairly common for BCDs to have integrated weight systems. They usually consist of a removable weight pocket on the front side of the BCD attached to the cumber bun. 

These can be used in lieu of a weight belt. Essentially you insert the needed weight into the pockets and then insert the pocket into its slot in the BCD. You can use both solid and beaded weights with these pockets.

Weight Pockets on Tank Bands and on the Back of BCDs.

Weight pockets are often added to BCDs, usually on the back side to allow divers to add weight in other areas besides their waste to help with distribution and trim. They can be an integral part of your weighting because, in addition to providing needed ballast, they also allow you to improve your trim. They can also be added to the cam bands on your BCD should your BCD not have the pockets built in.

Backplates

These are normally used in conjunction with a harness and wing. In recent years, there have been a few more conventional BCDs that have been modified to use back plates as well.

There are generally two types of back plates, Steel and aluminum. Which you should use depends on your weighting needs and the type of diving you are doing. Steel back plates are generally heavier than aluminum and thus provide more negative buoyancy. 

How much negative buoyancy they provide depends on the manufacturer, so it is important to find out how negative a backplate is in the water before you purchase it to ensure you are getting the best one for yourself.

The biggest positive attributed to back plates when weighting is concerned is the fact that they tend to distribute weight evenly across your back which provides more stability in the water by helping to placing your body in a horizontal body position. This is a huge advantage because having better trim reduces drag. This reduction in drag causes you to work less when under water which causes you to burn less gas and enjoy longer, less tiring dives.

There are two aspects to back plates that can be considered negative depending on who you ask (more about this later). First, backplates are a permanent part of your BCD and cannot be ditched in an emergency scenario (see the section on “ditchable” weights if you want to learn more about this). Second, the vast majority of jacket- style BCDs will not allow you to use a backplate. This is something to consider if you are thinking about switching to a back plate.

A note on Ankle Weights

While not as common as the other forms of ballast, there are people who use ankle weights when they dive. This is especially common when using a dry suit.

I do not recommend that divers use ankle weights. They make it more difficult to kick properly which negatively affects your efficiency under water. Their negative effects far outweigh any positive effect they can have in your trim.

The idea is that they help with keeping your feet down. When diving dry, air can become trapped near the legs and cause your feet to become positively buoyant.

If you feel you need more weight at your feet to help with trim, my recommendation is to look for a heavier fin, use one of the many wraps that are available to place around your lower legs to prevent gas from traveling to your feet. Or simply work on placing less gas into your dry suit. Having excess gas near your feet is a common beginners mistake when learning to dive with a dry suit.

Can you figure out how much weight you need using a calculation?

“Ten percent of your body weight!”

There is a common misconception with some people that you can use a formula to figure out how much weight you need in order to dive. One such formula which is the old “ten percent of your body weight” myth.

The truth is that there really is formula you can use to accurately calculate how much weight you are going to need when you dive. The only real way to do this is to get in the water and do a buoyancy check. The video below explains how to do a buoyancy check for yourself. 

How To Do A Proper Buoyancy Check: Part 1

How To Do A Proper Buoyancy Check: Part 2

Once you know how much weight you need for yourself, now you can determine the amount of weight you need for your gear. 

Do your ballast requirements ever change?

As stated in the previous section, only a buoyancy check can determine exactly how much weight you are going to need on a given dive. The reason why is because that number varies depending on several factors that we will go over in this section.

  • Your Gear: The equipment you use will certainly impact the amount of weight you are going to need when you go diving. When diving with a 5mm wetsuit, you are going to need more weight than when you diver with a dive skin or no exposure protection, simply because the thicker suit is more positively buoyant. The same is true if you switch from diving an aluminum tank to a steel tank or vice versa. Also, if you carry additional gear into the water such as reels, lights cutting devices etc.… All this equipment adds up and will affect the amount of ballast you need in the water.
  • Shell Dry Suits: A shell dry suit is a suit designed to keep a diver dry which does not in and of itself provide thermal protection. Shell dry suits require undergarments that give you the desired thermal protection based on your needs and the water temperature. Because these undergarments tend to be more positively buoyant the thicker they get, you will need to adjust your ballast needs accordingly.
  • Your body: Your buoyancy characteristics can change if your body composition changes. Let’s face it, sometimes we let ourselves go and we gain fat. Perhaps at other points in our lives we go on a diet and lose some of the unwanted fat. These changes in your body composition can affect your weighting needs. The more body fat you have, the more weight you need to achieve proper buoyancy.
  • Your Diving medium: Are you diving in fresh or salt water. Are you diving in an area that is known to have more salinity than the regular ocean? These things will affect your ballast needs. You will need to use less weight when diving in fresh water than when you are diving in the ocean. Diving in an area that is known for heavier salinity, The Dead Sea or Salt Lake come to mind.

Variables Which Will Change During the Dive

It’s important for you to know that in addition to needing to change your ballast requirements according to your gear, your exposure protection, fluctuations in your body composition and changes between salt and fresh water, there are also factors which could change during the dive.

  • Lung volume affects your buoyancy. The larger lung volume you have the more buoyancy shift you will feel as you inhale and exhale while you are diving. You can control this by thinking about how you breathe. By taking shallower or deeper breaths, you can make pinpoint adjustments to your buoyancy without having to make ballast changes. This is an important note to make since breathing deeper or shallower can affect your buoyancy throughout the dive.
  • Neoprene compression: When diving a wetsuit or neoprene dry suit, it is important to understand that neoprene compresses at depth. This is not so noticeable with wetsuits that are 3mm or less, however if you are diving with a 5mm or 7mm wet suit this fact is important, especially if you are diving deep (over 66 feet or 20 meters) where the neoprene will compress significantly. 

    This causes a change in its buoyancy characteristics. The thicker your suit, the more this becomes a factor. When selecting your ballast requirements, you must consider the suits buoyancy before the neoprene is compressed as well as after it compresses. We will get into more details as to why this is important when we go into the topic of ditching weights later in this article.

What About “Ditchable” Weights? Don’t All Weights Need to be “Ditchable”?

Most of us were taught in our entry level SCUBA course that we need to be able to ditch all our weight quickly so that we can properly manage an emergency.

When you think about it, it sounds like it makes sense. If there is an emergency underwater and you need to bring yourself or another diver to the surface, ditching the weight may make it easier since there is less ballast to bring up. This is especially true if the diver is unconscious and wearing a lot of lead. It is also easier to establish buoyancy on the surface when there is less ballast.

Now, before we move on, let me ask you something. In the above scenario, why does ditching the weight make everything easier?

I’ll give you a moment to think about it…

Do you know why?

It’s because most of the time the diver is over-weighted!

If a diver is properly weighted, it means that they are carrying just enough ballast to remain neutral at the end of the dive with the reserve pressure in the tank.

Think about it this way, if your tank is 3lbs positive at the end of your dive, you are going to need to add 3lbs of ballast to your rig to offset that change.

Now, let’s look at this using the example of a diver using an aluminum 80 (12 liter cylinder).

The weight needed to offset the positive buoyancy an empty aluminum 80 (12 liter tank) is around 4 pounds (1.8 kg) in salt water. Of course, it is highly unlikely you will ever dive with a completely empty tank.

At its working pressure, an aluminum 80 is about 2lbs (.9 kg) negative.

This means that, if you are properly weighted, you should at most be 6lbs (2.7kg) negative at any point during the dive.

6 pounds (2.7 kg) is NOT a lot of weight. Every BCD or wing on the market that can easily offset that amount of weight. It’s also an amount of weight that any diver should be able to swim up easily even if you were to have your BCD fail on you and not able to hold air.

Why am I saying this?

Because for many divers taking the weight off of their weight belt and distributing that weight either through weight pockets on the tank bands, a stainless steel backplate, or even by using a steel tank instead of an aluminum tank makes a lot of sense.

Distributing your weight around in this manner makes you more streamlined and puts you in a horizontal body trim position when you dive.

The bottom line is that, as long as you are not over weighted, whether your weight is ditchable or not will not be a big deal.

NOTE: There is an exception to this and it’s when you are diving in cold water and using a thick (7mm or more) wet suit or diving a dry suit (more on that later).

Why Ditching Your Weights Can be Dangerous!

What if you really need a lot of ballast to dive?

Maybe you dive in cold water. If you do, I know, you need quite a bit more ballast than if you are diving in warm water. Using a thick wetsuit or a drysuit is very different than diving a 3mm wetsuit on a tropical reef.

Perhaps you just need more ballast because your anatomy requires it.

Either way, when you do a proper buoyancy check, you’ll know that you are diving with the amount of weight you need to offset the positive buoyancy of yourself and your gear.

As a rule of thumb, if that amount exceeds 8lbs (3.6kg) the practice of placing all your ballast either on your weight belt or in the ditchable pockets of a BCD while at depth can be dangerous.

You may be wondering why. It’s because, if you were to ditch all that weight at depth, you could possibly be placing yourself into a situation where you could go into an uncontrolled ascent the moment you lose all the ballast that was keeping you down.

Uncontrolled ascents can have catastrophic effects on a diver.

Things like an arterial gas embolism, decompression sickness, or a reverse block are all real dangers. There is also the danger of being finding yourself in an uncontrolled ascent while hearing the sound of an oncoming boat.

If you still choose to store all your weight in a system that makes it ditchable, you need to think about the possibility that you could accidentally lose all your ballast.

I’ve seen this happen many times over the years. A belt becomes loose or the Velcro that holds a weight pocket in place becomes worn and doesn’t hold as tightly any more. This could cause a diver to unknowingly lose all their weight.

The bottom line is that if you need a lot of weight to be neutral at the end of your dive, suddenly losing that weight can be dangerous. You need to think about where you are placing the weight that you need and why you are doing so.

When You Absolutely Should Be Able to Ditch Your Weights!

There is one scenario where you absolutely need to be able to ditch SOME of your weight. It’s when you are diving deep (over 100 feet / 30 meter) and using a wet suit that is 5mm thick or more.

Why? Because the wet suit will compress at depth. Neoprene is a material that is made up of microscopic nitrogen bubbles. Those bubbles compress the deeper you go.

This means 2 things:

  • Your wet suit will not insulate as well at deep depths as it does at shallower depths.
  • More importantly, because all those tiny microscopic bubbles are compressed, the suit will also be less buoyant at depth.

Because of this, you’ll need to compensate for the positive buoyancy that your suit loses at depth by adding gas to your BCD. It also means that you are more negatively buoyant at depth than you are when you are shallow.

Therefore, it is important for you to be able to ditch some of your weight at depth.

Should you experience a catastrophic event that renders your BCD useless, you may not be able to swim your way up to the surface because of the additional negative buoyancy caused by the compression of your wetsuit.

In this scenario, ditching some of your weight could save your life.

The above scenario poses a difficult decision. You may need to ditch some weight to be able to get to the surface but doing so puts you in a position where, once your suit becomes more positively buoyant, you could find yourself in an uncontrolled ascent.

Yes, it is a catch 22. The way I see it is, I would rather be slightly positive than extremely positive due to the fact that I had to ditch all of my ballast. This is why I think it is important to make only some of your ballast ditchable rather than all of it. The amount that you ditch should not exceed amount of buoyancy lost by the suit.

When Things Go Wrong: Abrupt Changes in Buoyancy

I have a confession to make. When I first started diving I thought that the chances of having a failure of your BCD or anything else that would severely affect your buoyancy was unlikely. Especially if you maintained your gear and always went diving with relatively new gear.

Boy was I wrong!

First, I had a dive where my own BCD broke at the elbow where the low-pressure inflator connects to the bladder.

About a year later I was doing a dive with a student and her high-pressure hose burst while on the dive.

A couple of years after that, I had a different BCD’s dump valve completely come off when I pulled on it to release some gas.

Over the years I’ve heard multiple stories just like these that happened to other people.

I’m telling you this because, if you dive long enough, you will experience equipment failures. It’s a part of the sport. Fortunately, if you are properly trained these are usually just minor annoyances as they were for me and my student.

There are several scenarios where your buoyancy can change quite rapidly and without warning. As a diver, it’s important for you to know about and plan for the possibility of these scenarios.

Equipment failures that can cause abrupt Buoyancy changes

Catastrophic equipment failures are not common but they can happen and it is important to consider these unlikely scenarios and how to handle them.

Becoming Positively Buoyant Unintentionally

Burst disk failure: In the event that the burst disk on the tank valve fails you will be put into a potentially dangerous situation. Firstly, you will be losing the gas in your tank quickly. Your ability to breath will be completely compromised and they tank’s buoyancy characteristics will change very abruptly.

A free-flowing regulator:  Should a regulator fail and begin to heavily free flow, the rapid loss of gas can affect buoyancy. However, the effect will not be as abrupt as in the scenario above.

The high-pressure hose or SPG (submersible pressure gauge) can burst also causing a rapid loss of gas.

Becoming Negatively Buoyant Unintentionally

Wing Failure: Catastrophic wing failures have been known to happen. When wings fail in this manner, they tend to fail at the elbow of the low-pressure inflator or at one of the dump valves.  This renders the wing useless as a tool for buoyancy control.

A tear in the BCD is a possibility, however tears do not always render wings completely useless and are a lot less common. A leak in the bladder can also affect buoyancy, however the leak’s size and position may allow the wing to be at least partially useful as you ascend to the surface.

In any of the scenarios above, immediately ending the dive and ascending becomes of paramount importance. As we discussed earlier, controlling that ascent is also important because rapid ascents can cause all sorts of potentially life-threatening diving injuries.

The Case for Redundant Buoyancy

Being able to swim up without the assistance of the positive buoyancy of your bladder is something that every diver should consider. As we mentioned before, this is especially important if you are diving with thick thermal protection in cold water.

It is because of this that we recommend that you only dive with the amount of weight needed to offset your gas. This will make you just slightly negative in the event that you are in a scenario where your bladder is no longer functioning.

That being said, there are several avenues you can choose should you want to carry redundant buoyancy.

  • Redundant wings: There are wings that have two bladders in them. They are designed to offset each other in the even that one should have a catastrophic failure. They will require two low-pressure inflator hoses attached to two independent low-pressure inflators
  • A Dry Suit: A dry suit can be used as redundant buoyancy in the event of a catastrophic wing failure. This is because by adding extra gas into your dry suit you can make yourself more positively buoyant.
  • Lift Bag: This is the least desirable option. However, should you find yourself in a scenario where your bladder is no longer functioning, a lift bag can be used to offset negative buoyancy. If this is your only option, you must be aware that the bag cannot just be shot up to the surface from all depths and it is important to try to control the amount of lift the bag is providing you in this situation. Controlling buoyancy with a lift bag is not easy therefore it is the least desirable option.

Ditching Weight at the Surface

Many of us were taught that, if there is an emergency situation on the surface, we should ditch our weight as well as the victim’s weight. This is to establish positive buoyancy.

Every choice in diving has tradeoffs. If you dive a steel tank, a stainless steel backplate, or even some pockets on a tank band, you’re carrying some weight that may not be able to be ditched.

The tradeoff for not being able to ditch the weight is being more streamlined and having better body position in the water. Both of these allow you to have longer more enjoyable dives. You also avoid the negative consequences of losing your ballast at depth and having an uncontrolled ascent.

As mentioned before, as long as you are weighted correctly, the negative buoyancy created choosing to distribute weight in this manner should be minimal and easily compensated for by the BCD.

The real problem is that there are a lot of divers that are over weighted.

Ditching weights on the surface becomes crucial when a diver is over weighted. It’s when divers are over weighted that you MUST BE ABLE TO DITCH THE WEIGHT. Not being able to do so makes it difficult to establish positive buoyancy.

So, the bottom line is, if you dive don’t be over-weighted. If you have buddies who dive, don’t let them be overweighed, and if you want to help other divers become aware of this topic, make sure you share this article.

As you can see, there are many factors to consider when thinking about weighting.

Still wondering what ballast options are best for you? Use our buoyancy tool below to determine what kind of ballast will best suit your needs.

Did we miss anything? Do you have any questions? Please feel free to comment below!!

Click here to read more on how to figure out if you are correctly weighted: Are you over-weighted too? How much weight do I need for scuba diving?

Air Sharing: Why Your SCUBA Configuration Matters

By Carlos Sagaro

You're on a relaxing dive enjoying the beauty of the underwater world. You’ve left all your frustration and responsibilities above the surface. After all, this is where you come to “get away from it all,” right??

All of the sudden, you notice that another diver is swimming over to you wide-eyed and in a hurry. They give you the “out of air” hand signal just as they take their regulator out of their mouth.

This is where all your training and the choices you’ve made about how you configure your gear come into play.

How will you deal with this scenario? Is the way you’ll handle it optimal? Can you go through the motions in your mind’s eye right now and feel confident you are ready to handle an exasperated out-of-air diver?

When it comes to sharing air, there are many different configurations that divers use.

If you’ve ever wondered why different divers configure their primary regulator and their octopus different ways, and what the pros and cons are of each configuration, you’re going to want to read on because in this article we are going to touch on exactly that!

Disclaimer: Before beginning our discussion on air sharing techniques and configurations, it’s important to note that air sharing, especially in an emergency, is a skill that must be mastered in confined water under the supervision of a qualified SCUBA instructor. Do NOT SWITCH YOUR CURRENT CONFIGURATION without proper training and coaching from a qualified SCUBA instructor!

The origins of air sharing

When SCUBA diving was still new and considered by some to be an “extreme” sport, the gear that was used wasn’t nearly as advanced as it is today.

Early SCUBA rigs only had one primary regulator to breathe from. If your buddy ran out of air underwater, the only option was to share your only regulator by passing it back and forth between you and your buddy. Essentially, you’d take turns taking breaths from a single regulator.

As SCUBA equipment became more advanced a redundant second stage was added. This redundant second stage, which is commonly known as an octopus, could be given to an out-of-air diver independently. Now both the out-of-air diver and the diver donating the air supply could breathe simultaneously from the same tank.

With the ability to have 2 divers breathing from the same tank come many questions about how to best configure your gear. The first question being….

Which regulator should you give a diver in distress?

Before we can address the issue of how to configure your regulators, we need to discuss the major philosophical difference in opinion that many SCUBA instructors have.

You see, some instructors believe that an out-of-air diver should always receive the regulator which the diver that’s doing the rescue is breathing from, also called the primary regulator.

Others believe the out-of-air diver should receive the octopus.

While there is not “right” answer here, let’s take a look at some of the pros and cons of each method.

Some of the pros of donating the primary regulator (the regulator the diver is breathing from) include:

  • The shared regulator is usually the higher performing regulator:  The out of air diver is likely to have a higher breathing rate because of the nervousness / anxiety cause from being out of air.
  • It puts the diver that is donating the air source in control of the situation:  This means that the diver who is less likely to be in a panicked state becomes the dive leader.
  • Because the regulator being shared is the one the diver is breathing from, it needs to be on a longer hose:  This allows for the octopus to be on a shorter hose and reduces the chances of it dangling along and getting caught on the reef.
  • This configuration is usually more streamlined.
  • If an out-of-air and panicked diver rips the functioning regulator out of your mouth, you can instinctively reach for your alternate regulator which is what you would breathe from under this scenario anyway.

The cons of donating the primary regulator in a buddy-breathing scenario include:

  • It requires more skill / training to share air in this manner then using an octopus for a distressed out-of-air buddy.
  • When using an air2 or other similar regulator that serves the dual purpose of an inflator and a secondary regulator, that secondary regulator may not be as high performing as the primary.
  • Because the out-of-air diver needs the diver donating the air to participate, it is more difficult to simply grab an octopus and begin breathing without the assistance of the diver with air: This will make it more difficult for the distressed diver to get to his or her much needed air.

Diving with an octopus to give out as the alternate air source is probably the most common configuration.

The pros of giving out the octopus to an out-of-air buddy include:

  • Because the donating diver does not need to actively give up his or her regulator, the person who is out of air can gain access to the gas without having to rely on the donating diver’s skill level or proficiency.
  • The diver that is donating the gas never has to take the regulator they are breathing from out of their mouth.

The cons of giving out the octopus to out-of-air buddy include:

  • Because the octopus is on a longer hose and is rarely used, it is more likely to dangle or get caught up on a reef or a wreck.
  • Because it can dangle behind a diver, if a leak or free flow occurs at the 2nd stage it can go unnoticed for far longer than it would with other configurations.
  • Many of the octopus regulators on the market are meant to be cheaper and thus have more breathing resistance. Giving a diver who may already be panicked because they ran out of air a poor performing regulator may aggregate their panic.

Now that we understand some of the pros and cons of using an octopus for an out-of-air diver vs. giving them the regulator you are already breathing from, let’s look at some of the different configurations.

Configurations where you give out the octopus to an out of air diver

The placement of the octopus holder should be somewhere in the “safety triangle”. This is an imaginary triangle that goes from your chin to your waist in front where the octopus can be easily accessed by both the diver and their buddy.

Having the Octopus on a holder

There are many different types of octo holders on the market. Each design has their benefits and drawbacks. The basic premise behind all octo-holders is the same.

They must hold the octopus securely throughout the dive so that the regulator does not accidentally become dislodged and begin to dangle. They must also simultaneously be easy to deploy and come lose if it is needed for an emergency. (IMAGE of Octo holder)

Because of this dichotomy, many octo-holders fail and end up having a diver dangle their octo behind them damaging both the regulator and the reef.

BCD with integrated Octo-holder

Some BCD manufactures have taken note of the issue of keeping the octopus nice and tidy while still making it easy to deploy in case of emergency.

To help solve the octopus dilemma, they’ve designed their BCD’s to hold the octopus for you.

Using a D-ring as an octo holder

Yet another creative way to solve the octopus dilemma is to curl it into the D-ring of a BCD.

While this solution is less likely to result in the regulator becoming loose and dangling behind the diver, it does take a bit of getting used to.

Also, it may seem awkward to have the curled-up hose dangling below the D-ring where the octopus is stowed.

Configurations where the primary air source is donated

Air 2 (Regulator Low-Pressure Inflator Combo)

One of the most common configurations where the primary air source is placed on a longer hose and donated is when a diver is using an Air2 or similar inflator / regulator combo.

There are several low-pressure inflator / regulator combos on the market, but the SCUBA Pro Air 2 was one of the first systems that gained widespread use.

By combining the low-pressure inflator and the alternate air source into one, the diver effectively eliminates one hose from their SCUBA rig.

You also eliminate the possibility of having the octopus dangle because the hose used for the low-pressure inflator is typically much shorter than that of an octopus.

As mentioned before, the downside is that it requires the diver to be more involved in an out-of-air scenario because the must give out their primary regulator.

Because the hose on the Air2 is short, it makes it very awkward and less than ideal to be donated to another diver for air sharing.

Hogarthian set up (long hose tech diving set up)

The final configuration worth mentioning is one that was born in cave / technical diving but has been adopted by many recreational divers.

It is known as the Hogarthian rig named after Bill Hogarth Main.

The rig consists of the primary regulator being a longer hose (up to 7 ft) curled around the diver’s body. The octopus is worn on a necklace right under the diver’s neck.

In this configuration the octopus never comes off the necklace. In an emergency, the diver donates the longer hose and then switches to the octo.

Some advantages to this system include:

  • Most divers using this configuration opt to have 2 high performing regulators on your rig which eliminates the low performing octopus other divers use..
  • It eliminates the possibility of a regulator ever dangling because it’s nearly impossible for the octopus to come loose from the necklace..
  • If a diver ever approaches you in an out of air scenario, you can give away your primary and have almost instant access to your back up.
  • Because this set up often uses a much longer hose, it will give you the freedom to have some more space to move should you ever have to share air.

The only real downside to this configuration is that it does require training and practice in sharing air using this configuration. Also, if using a long hose for the primary, it does require extra care to not drag the primary regulator on the floor since it is on a very long hose.

Below is a Video where we discuss Air Sharing in Different SCUBA Configurations:

What configuration do you use and why? let us know in the comments below.

Nautilus Lifeline Marine Rescue GPS Review

By Carlos Sagaro

You're on a dive enjoying a beautiful reef. The time finally comes when you've consumed your gas and you and your buddy ascend to the surface. Once you break the surface you realize that you're are faced with the nightmare scenario every diver dreads...The boat is gone!

Maybe you just can't see it. Several minutes go by and you realize this is not the case. Maybe they had an emergency, surely another boat will come pick you up.

An hour and a half later you realize that's just not happening. What now? You and your buddy are stranded at sea and you haven't seen a boat for hours. That fancy SMB that can be seen several feet out of the water is useless, same goes for your whistle, they're only good if there's a boat nearby and looking for you. 

SCUBA divers navigating wall

I realize that this is a situation most of us don’t care to think about. Let’s face it, most of us dive to escape reality and relieve the stress we experience in our lives. Unfortunately, this scenario is more common than we want to admit. Being a SCUBA instructor, I read several stories about lost divers every year. Sadly, these divers are not always found before it is too late.

What if I told you there was a product available that could ensure that if, god forbid you ever found yourself on the surface all alone, you would not be left hoping that someone would come get you.

Say Hello to The Nautilus Lifeline Marine Rescue GPS

Nautilus Lifeline Marine Rescue GPS

The Nautilus Lifeline Marine Rescue GPS (Nautilus Lifeline for short) is the device divers have been waiting for years! 

It's is a personal signaling device made just for divers.  It's small enough that you can fit in your BCD pocket or on your SCUBA rig using the optional pouch. This allows you to take it with you on every single dive.

This is the first device of it's kind that can actually ensure that you'll feel secure knowing that you will always make it back to your friends and family no matter what happens on your dives.

In the event that you are lost at sea, the Lifeline allows you to send out a signal to commercial vessels, private yachts, military vessels and the Coast Guard that travels up to 34 miles. This signal will send your position and let any vessels in the area know your position so you can be picked safe and sound.

The truth of the matter is that we are not 100% in control of our destiny when we go in the water. No matter how diligent we are as divers...

There are things that happen that are out of our control!

Things like storms and a change in wind speed can affect surface conditions making it more difficult for dive operators to see you on the surface. Also, changes in current and visibility could make it difficult for you to get back to the boat, especially if you are diving off a private boat. Not to mention an emergency on the dive boat or even a dive operator forgetting you are in the water. All of the above has happened to divers over the years, and these are just a few scenarios that could cause a diver to get lost at sea.

The scary part is that we have no control over these things. 

Just like the seatbelts and airbags in your car, the Nautilus Lifeline is there to protect in case the unimaginable happens. It is your insurance against the unexpected.

It is compact which means that it can easily be stored in a BCD pocket or you can attach it to a BCD strap using the optional pouch. The batteries on the Lifeline can last up to five years and are easily user replaceable. The CR123 batteries and be purchased at any drug store or even online.

As long as you keep the cap closed, it is waterproof to 425 feet. The cap should only be removed on the surface when you are ready to activate the lifeline. It is positively buoyant and waterproof in all surface conditions, even with the cap off. The Lifeline comes with a one-year manufacturer’s warrantee.

 

Feeling Lost During Your Dive Sucks! 

Discover The 8 Little-Known Tools You NEED To Take With You On Every Dive To Avoid Being Lost!  ( FREE GUIDE )

X

How Does It Work?

The Lifeline sends your GPS position to the Coast Guard, all commercial dive vessels and many yachts within a 34-mile radius. The signal is accurate to within 1.5 meters. It’s broadcast via AIS (Automatic Identifications System) and DSC (Digital Selective Calling) which are the two most commonly used nautical messaging systems throughout the world. This means that if you need to use it, all modern vessels equipped with a VHF radio will receive your distress signal.

Nautilus Lifeline GPS sends out a signal to all boats within 34 miles

What is included with the Nautilus Lifeline?

Nautilus Lifeline Review

It comes well packaged in a box with an antenna winding tool. The batteries and pouch are sold separately. You can see for yourself what's in the box as well as how the device works first hand in the unboxing video below. 

The Evolution of the Nautilus Lifeline

As mentioned earlier, this is truly a device designed by divers for divers. The video below shows the story of the Nautilus Lifeline Marine Rescue Radio (this is the first-generation Nautilus) and how the original idea for the lifeline came to be.

The device shown in the original video was the first generation of the device (technically it’s now called the “Nautilus Lifeline Radio”) It is discontinued and no longer available. The newest generation is called the “Nautilus Lifeline Marine Rescue GPS”.

First Generation Lifeline

Nautilus VHF Radio

The newest generation does not have a built in VHF radio. This is actually a good thing. The reason is because it means that the device is half the size, does not need to be registered, it does not require programming, and does not need to be constantly charged.

It makes owning and operating the lifeline extremely easy. You just take it with you on every dive, rinse it off with the rest of your gear, and change the batteries out every 5 years or so. It really doesn’t get much easier. When the latest generation was released, its creator was interviewed about the differences. You can see that interview below: 

How Much does all this peace of mind cost??

The price of the the Lifeline makes owning the device a complete no-brainer. It retails for $200 dollars however, you can purchase the Nautilus Lifeline Marine Rescue GPS here for just $179. Click the link to find our more!

I don’t think there is any price I wouldn’t pay if I were stranded at sea for even a short while. The peace of mind having a device like this gives you is priceless. It’s something every diver should own.

The Nautilus Lifeline Rescue GPS is a great for anyone who is active on the water.  Whether you are a SCUBA diver, free diver, surfer or an avid boater, it will ensure you will never feel alone on the water again.  It is also makes a great gift for anyone who loves being on the water!

I hope you enjoyed our review.  Feel free to share this article with your SCUBA diver friends and leave a comment below if you have any questions for us.

How To Prevent Losing Your Dive Gear – Choosing SCUBA Gear Clips

By Carlos Sagaro

Have you ever lost a piece of expensive dive gear? As divers we all experience this at one point or another. I remember how frustrated I was when I lost a reel on a dive in the Keys. I saw it fall off of my rig and sink to the bottom, powerless to stop it. $125.00 dollars lost…

If this has happened to you, then you are definitely going to want to read on because we are about to go over a few simple steps you can take to ensure that you never lose another piece of expensive dive gear again.

Why You Need to Clip Off Your Gear

As divers we carry multiple pieces of gear. Things like primary and backup flashlights, compasses, submersible marker buoys, reels, whistles, cutting tools, etc. The list is long.

Because we carry so much gear with us, it is essential that we clip off every piece of equipment that we take with us into the water. The reasons could not be clearer.

First, dive gear is expensive and none of us want to lose our hard-earned equipment.

Second, clipping off our gear is important to protect the underwater environment. By making sure that our gear is both clipped off and snugly stowed away near our bodies and in pockets when we dive, we are ensuring the survival of the underwater environment that we so dearly love.

Preventing “Danglies”

We are all familiar with danglies. It is the term used by divers to describe hanging gear. Maybe you’ve seen them on your own dives. You are swimming and you look at another diver who has an octopus or maybe a flashlight hanging low off of their BCD. Maybe you’ve even seen this gear clumsily crashing into a reef or wreck as you cringe in disbelief.

At Greatdivers we take the protection of the underwater environment VERY seriously. Because of this we teach all of our students how to properly stow away equipment so that it does not dangle and cause damage to the fragile underwater environment.

Over the years we have tried several things to stow gear to our BCDs but have found that tire inner tubes tend work extremely well. All you have to do is take a used tire inner tube (I got an old one from a local bike shop for free) and cut it into strips and use it to affix things like lights to the shoulder straps of your BCD.

Please check out the video below to see exactly how we do this and how effective it is at keeping gear stowed away nice and tight:

How to Set Up Your BCD Pocket

Whether your BCD has pockets attached to it or you have purchased a pocket that you strap on to the webbing of your harness, all pockets should be properly set up.

Yes it is true that pockets usually have zippers or Velcro that keep them closed, but that in and of itself is not always enough. It not uncommon for divers to reach into their BCD pockets, go to take something out and accidentally lose a piece of gear in the process.

This is why we configure our pockets to ensure that we never lose a piece of gear when we reach in to retrieve our compass, reel or any other piece of gear stowed away inside of it.

We do this by looping a piece of bungee cord inside our pocket. By doing so we can clip off all the gear in our pocket to the cord so that we can easily have access to anything inside the pocket without accidentally losing another piece of expensive equipment. The short video above illustrates how we do this so please take a minute to check it out.

The Different Types of Clips

There are several different kind of clips that divers use to attach their gear to their BCDs. In this section we are going to review the two we recommend and one that we think is dangerous and no diver should ever take with them in the water.

Bolt Snap

Bolt Snaps: these are the most common clips we use with our gear. They are easy to use and can easily be attached to gear. It is important to note that they must be thoroughly rinsed and should be lubricated from time to time to prevent them from rusting.

Trigger Snap

Trigger Snaps: These are also extremely common for divers to use and are highly recommended in colder environments where heavy gloves need to be worn. This is because their design allows easy access when using heavy gloves. Even though these are less likely to rust than bolt snaps they should still be rinsed out thoroughly and lubricated on occasion

Carabiner

Carabiners: We do not recommend that you use carabiners to attach your gear. Their design allows them to easily be clipped off to your d-rings but they also have a fundamental flaw in that they can easily clip off to monofilament line that is often found underwater. This can cause a diver to get tangled and can create a dangerous situation. It is for this reason that many divers call these “suicide clips” and why we DO NOT recommend you use them to clip off your gear.

How to Tie Your Clips to Your Gear

Most SCUBA equipment comes with loops that are designed to allow divers to tie clips to it. One question we get asked is what we use to tie the clips to the equipment.

We recommend braided nylon line. There are two reasons for this. First it is easily accessible since most dive reels and spools come with the line. In our experience these reels usually have more line that you need and it is not difficult to take a few feet and use it  attach clips to gear. Secondly, this line is EXTEMELY resilient underwater.

We do not recommend that you use tie wraps to affix gear to clips. Tie wraps tend to deteriorate after repeated exposure to salt water and can fail. This happens quite often.

Below is GIF showing exactly how we tie clips to gear. Please take a minute to watch it so that you can ensure that your dive gear remains with you for years to come.

If you found this post useful, just click below to download our free guide “The 8 Navigational Tools you should Never Dive Without.” In it we go over 8 little known tools you can use to help you navigate while you are underwater.

 

Feeling Lost During Your Dive Sucks! 

Discover The 8 Little-Known Tools You NEED To Take With You On Every Dive To Avoid Being Lost!  ( FREE GUIDE )

X

SCUBA Mask Fogging up? How to Defog Your SCUBA Mask

By Carlos Sagaro

How to Prevent Your SCUBA Mask from Fogging Up

It has happened to all of us at one point or another. We have arrived at our dive site! We have been anticipating this for some time. The reef is waiting to display its opulence of life. The Crew gives us their briefing. We don our gear and are anxious to get in and enjoy the view. We enter the water and begin our descent into the abyss, and then it happens…OUR MASK FOGS UP!!!

It’s too late to go back now, we know that we will spend the rest of our dive with a foggy mask because we did not follow the right procedure to ensure that this does not happen. While it is not a serious situation, a foggy mask causes an inconvenience that it is impossible for us to ignore.

​Don't worry though, in this article you are going to learn a new scuba mask preparation procedure that will ensure that this does not happen to you ever again. Keep reading so you can learn what you can do to make it so you never dive with a fogged up mask again.

scuba mask fogging up, SCUBA mask anti fog, defog scuba mask

Mask Preparation: The Key to a No Fog Mask

***Disclaimer***

Different manufacturers have different processes that they use in the production of their masks. Before you do anything to your new mask, you need to read the instructions that come with it. The procedure that will be detailed below does not apply to masks that come factory-applied defog or no fog masks.

scuba mask fogging up, SCUBA mask anti fog, defog scuba mask

Mask manufacturers often spray their masks with silicon during the manufacturing process to protect the mask skirt as well as the glass. In many cases, this silicon spray is not removed as it also protects the mask during shipping. The problem is that, if not removed before diving, this silicon spray will make it practically impossible to stop your mask from fogging up. The best anti-fog spray for scuba masks in the world will not make a difference if you do not pretreat your dive mask.

The way we at Greatdivers suggest that you remove this spray is by cleaning your mask with toothpaste before your first dive. Cleaning the SCUBA mask the first time in this manner will make a huge difference in your ability to prevent it from fogging up.

Below is a video explaining how to do this:

Pre-dive Ritual that Prevents Your SCUBA Mask from Fogging Up.

Even if you clean your mask like we did in the video above, you will still need to apply some sort of SCUBA maskanti fog so it does not fog up. There are several liquids you can apply to your mask that will help you achieve this.

  • Antifog Spray: There are plenty of commercially available defogs you can use to prevent your mask from fogging up. The way they work is simple, you apply the solution to the inside of your mask and rub it in. You rinse off the excess and the residue leaves a film on the mask that prevents it from fogging up.
scuba mask fogging up, SCUBA mask anti fog, defog scuba mask

  • Baby Shampoo: Many people swear by this. A diluted solution of baby shampoo can be used in the same manner as the defog above. Divers who use this like it because it is designed not to irritate the eyes.
scuba mask fogging up, SCUBA mask anti fog, defog scuba mask

  • Spit: For many divers, spit is their method of choice. It is effective, ready-available and it most certainly does not irritate the eyes. Some people are not a fan because they are grossed out by the idea of using spit asdefog. I will admit, this is my method of choice and I do not mind a "spit mask."
scuba mask fogging up, SCUBA mask anti fog, defog scuba mask

I would like to mention one last thing, I have never been a fan of using mask buckets on dive boats. Often times they contain dish soap which can be extremely irritating and this is made worse when every other diver on the boat dunks their mask into the bucket. If you are going to use the mask bucket, I highly recommend that you try on your mask before you get in the water to make sure that it does not irritate your eyes.

What is your preferred method of dealing with a foggy mask?

Scuba Tank

Aluminum vs. Steel tanks: How Heavy is that SCUBA Tank?

By Jose Cernuda

What 2 metals are SCUBA tanks made of, Aluminum vs. Steel tanks, How heavy is a SCUBA tank

What kind of tank do you use when you go diving?  The size of the tank and whether it's made out of steel vs. aluminum will hugely influence how much weight you'll need to take with you on your dive.   Many divers think diving with one type of tank is better than diving with another.  The truth is that the type of diving you do, where you are diving and even the thickness and type of exposure protection you use can play a part in your choice of SCUBA cylinder.

In another post, we talked about the importance of buoyancy checks and determining exactly how much weight you need in order to make your body neutral underwater.  Besides your body and your gear, you have to compensate for your SCUBA tank as you dive.

What 2 metals are SCUBA tanks made of?

Aluminum Vs. Steel Tanks

You may be asking ” how heavy is a SCUBA tank,” but the real question is how buoyant it is.  Different tanks have different buoyancy characteristics.  As divers we need to be aware of the buoyancy characteristics of the tanks we use when we dive.  This is important because it determines how much weight we need when we go diving.  It is also good to know because we can use tanks to replace ballast depending on our weighting needs and diving conditions

There are two types of SCUBA tanks for divers to choose from.  Aluminum SCUBA tanks tend to be negatively buoyant at the start of your dive when they are full.  However, as you dive, these tanks tend to become neutral and can even be positively buoyant by the end of your dive. Because of this, you have to consider the tank’s positive buoyancy at the end of your dive when determining how much weight you will need.  

Both steel and aluminum SCUBA tank sizes vary.  Different tank sizes have different buoyancy characteristics.  For example, a steel 120 SCUBA tank will have different buoyancy characteristics than a steel 80 SCUBA tank.  Not only do sizes affect their characteristics, whether it is a high pressure SCUBA tank or a low pressure SCUBA tank makes a difference and so does the tank manufacturer. Faber tanks specs are not the same as Catalina or Luxfer tanks.  It is important to research these differences when choosing your tanks.

Steel SCUBA tanks tend to be negatively buoyant throughout your dive.  So when diving with steel tanks, you will not need the same amount of weight.  It is important to keep in mind that the buoyancy characteristics of steel tanks also change throughout a dive.  So while a steel tank might be very negative at the start of a dive, it can become closer to neutral as you dive.

We did a quick video below to illustrate the point. It’s a cool little experiment you can try with different cylinders and see what the buoyancy characteristics are.

What cylinder do you dive with and why?  Please feel free to comment below, we would love to hear from you!