The size and type of cylinder you use for diving is one decision most divers wrestle over, and with a good reason. The diver’s cylinder most often determines what type of BCD, regulator first stage, weighting, and exposure protection a diver uses. Heck, it even defines what kind of diver you are and the type of dives you do in most cases. The main considerations for a diver in selecting a cylinder are the material, capacity, and valve connection type. So in the spirit of the crew here at DRIS being ever helpful, let us tackle them one at a time.
First, let’s look at cylinder material. The two main ones we have here are steel and aluminum. Both have strengths and weaknesses. Aluminum tends to be lighter, inexpensive, and more widely found around the world as a rental. You can usually pick up 2 aluminum cylinders for the price of 1 steel, and if your gear is set up for diving with aluminum cylinders you can be assured the ability to destination dive with minimal gear adjustments. The trade off is that aluminum cylinders tend to require more weight to offset positive buoyancy and come in limited capacities. Steel cylinders, while more expensive than aluminum tend to be more robust, come in a wide array of sizes, and in most cases require 6-8 less pounds of lead on the diver’s weightbelt. The inherent negative buoyancy of the steel cylinder usually makes it an ideal option for cooler water diving where thick exposure protection is a necessity.
Next, let’s tackle cylinder capacity. This depends on the type, duration, and depth of diving you traditionally do. In aluminum cylinders you are limited to a few sizes, with 63, 80, and 100cf being the most common. With respect to steel cylinders you have more choice in capacity with the common ones ranging from 50-149 cubic feet as well as the option of low pressure(LP), and high pressure(HP) units. If you’re going into the technical or techreational realm of diving double cylinders come into play for twice the capacity of a single cylinder.
Last but not least is the determination of connection/valve type. The two main connection types here are DIN and Yoke. Both are rather common but most destinations that supply rental cylinders for recreational diving use the Yoke system, while technical divers often opt for the DIN system. Luckily, nowadays it is rather easy for a diver to be able to switch between the two. With the combo valve, going from DIN to Yoke is as simple as removing a small plug in the valve with an allen wrench. For divers who own DIN regulators and need to make use of Yoke tanks, a screw on adapter is a viable option.
As you can see, cylinder selection has quite a few considerations and can even go so far as to define the type of equipment you own and use. The prudent diver needs to take a look at the type of diving and conditions when making a selection for either purchase or rent. As always, the team here at DRIS is here to help with any questions you may have.