For cylinders & valves for rebreathers, visit our CCR Cylinders & Valves page.
What Happened to Low-Pressure (LP) Cylinders?
Many experienced divers have traditionally preferred low-pressure cylinders because they are easier on regulators, have no short-fill concerns, and are more suitable for partial-pressure blending. However, with a few minor exceptions, we no longer offer primary low-pressure cylinders.
The old low-pressure DOT 3AA design cylinders (2640 psi, i.e., 2400 with a +) are being replaced by modern high-pressure DOT SP design cylinders (3442 psi, no plus needed). That's because you can use the high-pressure 3442 psi cylinders as low-pressure 2640 psi cylinders if you prefer, simply by under filling. Manufactured from high-tech steel alloys, the 3442 psi DOT SP cylinders have similar lengths, diameters, and capacities at 2640 psi as the old 3AA low-pressure cylinders. Even better, the empty weight of the modern cylinder design has been reduced slightly, yet the buoyancy remains slightly negative when empty.
One idea we like is selecting a larger capacity cylinder and then deliberately under fill. For example the HP100 yields 89 cubic feet at 3000 psi, and 80 cubic feet at 2640 psi. That is plenty of gas for most dives, puts an end to short fills, and the lower pressure is easy on equipment, yet allows the option of a high-pressure fill when you need really need more gas. This is how divers have for years been using overfilling with low-pressure cylinders, but with the advent of the large-capacity high-pressure cylinders, it eliminates the concerns regarding overfills.