A Scuba diving cylinder is generally a steel or aluminium cylinder that holds air under pressures of 200 bar up to 300 bar. A cylinders operation is very simple to explain, it’s essentially just a very strong container with a on/off valve. For recreational diving you would generally just use the one cylinder for technical diving you can twin two cylinders using special valves and a manifold. For more information on Scuba Diving Cylinders read down, alternatively go straight to the Scuba Diving Cylinder department.
Which material should I go for?
Steel Cylinders – Steel cylinders are the most popular type of diving cylinder in the UK. This is due to their weight characteristics which give them negative buoyancy which allows you to have less weight on your belt (essentially they are heavy, therefore sink), the other positive to steel is it can handle higher pressures (up to 300bar) than aluminium. The obvious downside to steel cylinders is that they are heavy, the other downside is that without proper care they will rust over time.
Aluminium Cylinders – Being a softer metal than steel, aluminium tanks are more likely to suffer from damage than steel, another downside to being softer is that the walls of an aluminium cylinder have to be thicker, so to get the same litre cylinder the cylinders size must be larger. The advantages of aluminium cylinders is that they are lighter than steel cylinders and less susceptible to corrosion. However you should note that they get much lighter when empty underwater so due care should be taken to make sure you have enought to compensate towards the end of the dive.
What size cylinder do I need?
There are lots of different sized cylinders available, however for recreational diving you would generally choose either a 10ltr, 12ltr or in some cases 15ltr depending on your size. The choice for 90% of divers would be the 12ltr. However, if you are particularly small or large, then a 10ltr or 15ltr would be worth considering.
For technical divers who require a longer bottom time it takes more consideration. A general choice would be two 12ltr cylinders connected together with a manifold. However before purchasing you really need to consider how long you wish to stay down for.
Din or Yoke (a-clamp)?
This is a common question, however your choice whether to buy a Din or Yoke cylinder should be made based on your regulator. There are advantages to both valve types but in reality it comes down to what regulator you have. Want to look at regulators? Check out our Scuba Diving Regulator department.
Most modern cylinder valves are both din and a-clamp courtesy of a screw out section (all of our cylinders have this valve). This is the best valve to go for as it gives you the best of both worlds.
Please note Nitrox is now only available in M26 DIN so if you're going Nitrox you will only be able to get DIN regs and cylinders
Do I need a cylinder boot?
In the real world yes you need a cylinder boot. A cylinder boot gives your otherwise wobbly cylinder something to stand in and keep it upright. It also gives it a layer of protection against bumps and bangs. A worthwhile investment.
Cylinder Care
Handling – Keep your cylinder safe, the more hits they take the shorter their lifespan.
Keeping Moisture Out – Essentially if moisture gets in you are much more likely to get cylinder corrosion. The easiest way to avoid this is to keep your cylinder pressurised. Keeping some pressure in the cylinder will help to avoid this. When filling ensure that the compressor has at least two moisture filters. This should keep moisture to a minimum.
Tests – Once every 2 and a half years you need to have your cylinder tested, first a visual inspection, then a full hydrostatic test. Alternating every 2 and a half years. When tested they will receive a stamp with the test date on it. Without this test your cylinder cannot be filled. If you feel that your cylinder is looking a little ropey then have it tested, a defective or damaged cylinder is an extremely dangerous thing.
Cylinder Markings
What do cylinder markings mean? This diagram should help explain.
Government Approval – The DOT specifications is a countries mark that the cylinder meets the countries specifications for cylinders. For us in the UK this should read EN144/BS, they should also have a CE stamp.
Metal Type – This section notes the type of metal the cylinder is made from, for instance 3A stands for carbon steel. This marking is important for those testing the cylinder
Working Pressure – An important mark, this indicates the cylinders maximum working pressure, this can sometimes be in bar or psi, in this instance the cylinder marking indicates the cylinder can hold 2250 psi.
Serial Number – A unique serial number which all scuba cylinders carry, made up of lot number and size.
Manufacturer Identification – This is usually after the serial number and indicated the manufacturer. Examples of manufacturers would be faber, luxfer and PST.
Hydrostatic Test Date – This will show the last date that the cylinders hydrostatic test was done on. When its re-tested a stamp will be added to the cylinder indicating the last date. So if the cylinder is over 2 and a half years old look for the stamps.
