Whenever anyone takes up the sport of scuba diving it seems clear that there’s a good amount of equipment. Everything from masks to fins looks like it might add up to a fair amount of weight to carry.
Take a look at any diver and it’s easy to recognize there is a need for a lot of equipment, with both primary and redundant systems.
It’s not unreasonable to ask how much this all weighs, but it’s clear that the heaviest part of the kit will be the tank.
The question is, how heavy? The tank is the large metal tank used to carry the compressed air, but how much does a scuba tank weigh?
A typical scuba tank is 12 liters in volume and 230 bar pressure and unfilled will weigh around 16kg (35 lbs). The factors affecting weight are material, tank size, and pressure. A filled tank with compressed air and a valve will add around 3.5kgs.
A tank is easily the heaviest bit of kit regardless of whether it’s filled or not, with a full set of scuba gear weighing around 22 kgs.
Even though it’s a lot of weight, it’s land weight and in the water, with buoyancy, you should effectively be weightless.
There are a few scuba tank manufacturers who make precision tanks in different materials, capacities, and pressures. Steel and Aluminium are the most common materials with choices typically around 230 bar to 300 bar for the steel tanks.
Sizes can range somewhat, as can the various colors and aesthetics, but a 12L tank would be a standard size, or sometimes 80 cubic feet, which is 11.1L.
Below you will find a comparative table of manufacturers with their corresponding weights.
Anywhere between 14kg to 18kg is about right for a tank when scuba diving.
Does A Scuba Tank Weigh More Full?
Yes, all other things being equal a tank full of compressed air will weigh slightly heavier than an empty tank.
You might not be surprised to learn that it is quite calculable as well. That’s the nice thing about this science malarky.
There are some well known scientific formulae for calculating the gas weight, but for all situations, you might find yourself in;
Gas weight of air (in kg) = 0.0012 x pressure in bar x volume in liters
With these formulae, you can calculate how much above the base weight you will be carrying if the tank is filled.
- 12 liter tank at 232 bar is 0.0012 x 232 x 12 = 3.34kg of air
- 12 liter tank at 300 bar is 0.0012 x 300 x 12 = 4.32kg of air
- 11.1 liter tank at 207 bar is 0.0012 x 207 x 11.1 = 2.75kg of air
Thus if you add the empty weight of the tank, the weight of the calculated air, and the addition of the tank valve you will be pretty close to the weight of the tank.
Generally speaking, a full 12L tank with 232 bar will weigh around 20 kilograms.
Factors That Effect Weight Of A Scuba Tank
Several factors go into the total weight of a scuba tank.
In no particular order they are;
Full or empty – As we have just learned, putting compressed air in the tank will typically add around 3.5kg to the weight of a tank. As compressed air is used the weight of the tank will lighten up until it reaches its empty weight.
Tank material – Tanks will either be made from steel or aluminum. Steel is both stronger and more ductile, while both are extrudable. Thus for a given tank size and pressure, less steel is needed for containing the compressed gas.
Steel tanks will be lighter than aluminum tanks for this reason. For a similar 12L tank, an aluminum tank might be a few kilograms heavier.
Tank size – Nothing too shocking about this one, but the bigger the tank, the heavier it will be.
Pressure rating – Tanks are rated for pressure, most typically in bar or psi. A higher pressure rating means air at higher pressures can be stored. More air in the tank means a heavier tank. A 12L tank at 230 bar will be approximately 1kg lighter than a similar tank at 300 bar.
Valve – Often weights don’t include the tank valve, but these might be around 0.5kg or so in weight
Final Thoughts – Parting Waves
There’s no doubt that of all the equipment a scuba diver carries the tank is the heaviest bit of kit. They’re quite safe when handled properly, and are typically put on only when entry to the water is imminent.
While heavy on land, in the water a diver will essentially be weightless. So whether a diver uses a 300 bar 15L steel tank or a 12L 230 bar steel tank, the weightlessness in the water will be identical.
The weight of the tank is only important with respect to traveling and water entry.
While it can seem like a lot to carry about, the more accustomed you become to scuba diving the more you will get used to it. Weightlessness and weights to achieve buoyancy notwithstanding.
Weight is only an issue above the surface, for below the objective is to achieve neutral buoyancy.
The reality is that weight for a scuba tank isn’t really an issue for most scuba divers, as bearing the brunt of it doesn’t happen for long, and won’t affect most peoples scuba enjoyment.