Scuba Tanks
Water & Snow · 10 specs
Direct Answer
Scuba diving high-pressure cylinders and valves are regulated under ISO 9809 (Steel), ISO 7866 (Aluminum), US DOT-3AL/3AA, and EN 250. The world's most common recreational cylinder is the Aluminum 80 (AL80), with an internal water capacity of 11.1 liters (0.39 cu ft), working pressure of 3,000 psi (207 bar), and delivering 77.4 cu ft (2,192 L) of free air. Cylinder valves connect to first-stage regulators via two distinct standards: Yoke (A-clamp / INT; rated to 232 bar / 3,365 psi) and DIN (G 5/8" threaded connection; rated to 232 bar or 300 bar / 4,350 psi).
Source: ISO 7866 (Refillable seamless aluminium alloy gas cylinders) / ISO 9809 (Seamless steel gas cylinders) / US DOT-3AL / EN 250 · Last reviewed Aug 28, 2026
Specs
| Aluminum 80 (AL80) Free Air Volume | 2,192 liters (77.4 cu ft at rated working pressure) |
| AL80 Working Pressure | 207.0 bar (3,000 psi / 20.7 MPa) |
| AL80 Internal Water Capacity | 11.1 liters (0.39 cu ft internal volume) |
| AL80 Empty Tare Weight | 14.2–14.5 kg (31.4–32.0 lbs without valve) |
| AL80 Buoyancy (Full vs Empty) | -0.7 kg (-1.6 lbs sink) Full / +1.9 kg (+4.1 lbs float) Empty Seawater Buoyancy |
| High-Pressure Steel 100 (HP100) Pressure | 237.0–300.0 bar (3,442–4,350 psi / 12.9L water capacity) |
| HP100 Buoyancy (Full vs Empty) | -3.8 kg (-8.4 lbs sink) Full / -1.1 kg (-2.5 lbs sink) Empty Remains negative |
| Yoke Valve (A-Clamp / INT) | Max 232 bar (3,365 psi; clamp bracket over captured O-ring) Recreational Standard |
| DIN Valve Standard | G 5/8 in Thread (EN 144-2 / ISO 12209) 232 bar (5 threads) or 300 bar (7 threads) |
| Hydrostatic Test Cycle | Every 5 Years (at 5/3x working pressure: 5,000 psi for AL80) DOT / ISO Recertification |
DIN vs. Yoke Valves & Cylinder Buoyancy Shift
- DIN (Deutsches Institut für Normung) vs. Yoke Connection: The Yoke connection clamps over the outside of the post valve, leaving the rubber O-ring exposed to extrusion at pressures above 232 bar. The DIN valve screws directly into internal G 5/8" threads, fully encapsulating the O-ring for extreme pressure security up to 300 bar (4,350 psi) in cave and technical diving.
- Aluminum Buoyancy Shift (+4.1 lbs): An AL80 tank is negatively buoyant when full (-1.6 lbs) but shifts to positively buoyant (+4.1 lbs) as the diver breathes down the 2.6 kg (5.7 lbs) of compressed breathing air mass, requiring divers to calibrate proper end-of-dive lead ballast.