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.
- Difficulty performing a safety stop: Even if you decide to call your dive, you still should perform a safety stop. Unless you are holding on to a line, this can be very difficult.
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 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.
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!!