Steel TankA diving cylinder, scuba tank or diving tank is used to store and transport high pressure breathing as a component of SCUBA (Self-Contained Underwater Breathing Apparatus). It provides gas to the Scuba Diver through the demand valve of a diving regulator.

Diving cylinders typically have an internal volume of between 3 and 18 litres and a maximum pressure rating of 200 bar to 300 bar, (about 3000 psi to 4500 psi). The internal cylinder volume is also expressed as “water capacity” – the volume of water which could be contained by the cylinder. When pressurized, a cylinder carries a volume of gas greater than its water capacity because gas is compressible. 696 (3 x 232) litres (25ft³) of gas at atmospheric pressure can be compressed into a 3-litre cylinder filled to 232 bar. Cylinders also come in smaller sizes, such as 0.2, 1.5 and 2 litres, however these are not generally used for breathing, instead being used for purposes such as marker buoy, dry suit and buoyancy compensator inflation.

Valves – A K-valve, which comes on all aluminum tanks and low pressure steel tanks, do nothing other than release or stop the flow of air from the cylinder.

Din Valve – These valves are used on all high pressure tanks – 3300 PSI and above. Regulators used on HP tanks require that your regulator be converted to DIN.

If a diver wants the freedom to dive anytime, a tank is a must.  You can safely use a tank that was filled a week ago. Aluminum tanks are much lighter than steel tanks, but steel tanks take more punishment, and as a rule last longer.

Kathy Dowsett


About Kathy Dowsett

I believe in protecting our oceans, lakes and rivers, as well as their aquatic life. I respect the work of conservation groups such as Save the Sharks, Save the Sea Turtles and Save our Wrecks. I believe that the use of plastic bags/bottled water should be discouraged as plastic finds its way to the ocean. I also support Diving for the Disabled and Swimming for the Disabled. As a PADI-certified diver, my interest in diving led to the opening in July 2008 of kirkscubagear, my online business. My site offers more than 2,000 products, including freediving, swimming and outdoor equipment. My continuing goal is to encourage diving and offer customers a shopping alternative for the purchase of scuba gear.

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