When you go to dive centers around the world, you will usually encounter a dive master who is 100% certain that he knows exactly how much weights you really need. In many cases, he will be wrong! Don’t let him decide for you. He is likely to give you a default answer which might be wrong and misleading. Be responsible for yourself and put some thought into your lead!
To determine the amount of weights you need, to dive safely and comfortably underwater, you need a deep understanding of the subject. One thing is certain – Proper weights make you a better diver!
Let’s go over some of the misconceptions which are well spread around the world.
Take 10% of your body weight in lead
A common rule of thumb, adhered by many divers, claims that a diver must carry weights equivalent to 10% of his body weight. While that does give you a certain range of the amount of weights you need, it does not take many important factors into account.
Factors such as muscle, fat, height, gear and exposure suit are crucial when choosing weights and should be taken into account. For example, muscles sink and fat floats. A muscular man weighing 180lbs would probably need much less than 18 pounds of weight (even with a long 5mm), whereas a short stalky fellow weighing 180lbs might actually need more than 18lbs. This rule has actually led to many over weighted divers.
Don’t be overweight!
Most beginner divers, and even some of the more experienced I know, dive with too much weight, either consciously or without knowing. Very bad practice!
There is a common belief among new divers that it’s better to sink fast than to have a hard time going under. News flash! When using proper weights, it takes a few moments to sink! You don’t just drop like a rock.
Being overweight (aside from an extra 2lbs for the end of the dive which is fine), can lead to some dangerous situations. Sinking too fast is a common cause for ear problems, especially if you’re having trouble equalizing. You will also feel like you have to swim fast all the time, to stop yourself from sinking, causing you to drain your air, wear yourself out, or even lose the group/buddy – something I just witnessed a few days ago.
Too much weights also affect your body position, sinking your lower body and causing you to swim up. If swimming in deep blue without a reference point, there’s a good chance you will be swimming up, eventually leading to an uncontrolled ascent.
Even if you do manage to balance yourself properly, you will have much more drag through the water – again, leading to fatigue and exhaustion.
Don’t be underweight!
A common belief shared by experienced divers and even instructors is that using less weights means you’re a better diver and much more awesome in general. The less weights you use, the cooler you are!
Using less weights does not make you cool. Using the ideal amount of weights for you makes you cool! As well as a better diver in general.
What would happen if you don’t carry enough weight? The most obvious danger is becoming a “human corkscrew” during the dive and especially at the end of the dive. Whether diving with steel tanks or aluminum, at the end of the dive you are more positively buoyant, and as you ascend you are increasing the risk of popping up to the surface without being able to control yourself.
The best case would be swimming downward for the last 10 minutes of the dive, even during the safety stop, or having to hold your buddy or a rope to stay under. The worst case, well I guess that’s pretty obvious – rapid ascent, lung expansion, decompression sickness, baro chamber and more fun activities…
Swimming downward for half of the dive does not look cool, so don’t be brave and force your way down when starting the dive. It won’t end well.
What should you pay attention to when choosing the right amount of weights?
As I mentioned above, one of the most important factors are body fat vs muscles. I don’t want to sound chauvinist, but women have a higher fat percentage so the 10% rule of thumb might actually be close for most women, even the smaller ones. I’m saying that as a smaller woman J
That 10% rule basically applies when using a full 5mm long suit and diving with a steel tank. Even then, I would start from 8% and add 2lbs if needed.
* As long as we are discussing body fat, here’s a great tip for people with a healthy amount of belly fat – Wear your weight belt as high up as possible, to prevent it from loosening during the dive. If possible, use integrated weight systems.
Another factor we need to take into account is height. Taller people would be more positive, since they have more surface area when swimming horizontally, so they will need more weight.
The type of exposure suit you are using is another important factor. The more neoprene you are wearing, the more lead you will need. A new suit is much more positive than an old, worn out suit since the air bubbles trapped in the neoprene lose their volume over time.
When wearing a long 7mm suit, you need to add about 4.4lbs from the 10% rule and when using a 3mm you need to subtract 4.4lbs. This is another rule of thumb, stating that you should add 2.2lbs (1kg) for every 1mm of neoprene. Using the rule does not relieve you from checking your buoyancy after changing your weights! Rules only help to get a ballpark figure.
The type and size of tank greatly affects the amount of lead we need.
An Aluminum 80 tank has a buoyancy variation of about 4.4lbs between 3000psi and 700psi (200 bar and 50 bar). At the end of the dive, the tank will be positive. A Steel 80 tank would start negative and end negative, but lose about 6.6lbs of buoyancy throughout the dive. When diving in fresh water, we need to subtract about 4-7lbs from your usual salt water weights.
Another important factor is experience. The more experienced you are, the more you are in control of your breathing and the more calm you will be underwater. When you breathe wrong, your lungs tend to be filled with more air, hence you will need more weights.
The single most important improvement you can make to relieve yourself from excess weight is to STAY CALM. Relax. Take it eaaaasy…
Now that I know all the factors, how do I actually calculate the weight?
There are various calculators which can be found online. Some produce a pretty accurate number, but most tend to be too generous with the amount of lead recommended. I wouldn’t rely entirely on this option, but do use it as a ballpark estimate.
This is one of the most recommended ways and the easiest to perform. You can do the check before the dive and add/reduce weights as necessary, but the ideal check would be at the end of the dive.
How to perform a proper buoyancy check:
Before the dive, float motionless in deep water.
Deflate all the air out of your BCD.
Take a normal breath and hold it.
If you start sinking – you need less weight, if you find yourself bobbing out of the water – you need more weight.
Remember – Stay still! Do not move your fins or hands while doing the test.
Repeat the process until you are floating as close as possible to eye level.
Since this is a pre-dive check, you will need to add weight to compensate for the air in your tank. It’s usually 4-7 pounds depending on the tank you use. Check online or ask your dive instructor if you’re not sure.
This check can be done at the end of the dive with a near empty tank. If you are floating at eye level with an empty tank, that’s perfect. Just make sure there’s someone there to hand you weights or take them from you while you check your buoyancy.
Go By the Book
The most accurate method would be to calculate every piece of gear you use separately. But beware, it’s quite an exhausting process. If you dive with the same gear in similar conditions, it may be worth doing this once.
You will need to grab every piece of gear and perform a buoyancy check for it. Enter the water with your bathing suit and weights only and perform the above check. Then, do the same while wearing your wetsuit. Deduct the first figure to determine your wetsuit buoyancy.
Now deflate your BCD completely and add weights to it until it is neutral. Finally, throw in all your gear including fins, mask, knife, buoy and whatever else you’re carrying during the dive into a mesh bag. Add weights until the bag is neutrally buoyant. Add all figures, including the weight needed for the tank to get the precise amount of weight you will need.
After this entire test, if your buddy doesn’t hate you and still wants to dive, you should be perfectly weighted!
Ultimately, there is no magic answer. Each diver must recheck his weights once in a while, especially when switching gear, environment or just after a long dry period.
If you manage to determine your ideal weight amount, your dive would be more comfortable and enjoyable, keeping you fresh and happy after each dive. I guess that in the end, that’s what we all want 🙂
So… How much weights do you REALLY need?
Agree? Disagree? Do you have your own way of calculating weights before the dive? Let us know in the comments below!