Reference
Collected information on the equipment cave divers actually use. There is a definite Houston-area bias, openly acknowledged since the day this page went up.
Much of this material was contributed between 2000 and 2003. Physical data — capacities, dimensions, buoyancy — remains broadly useful. Vendor details, prices and links from that era largely do not. CAVEDIVER.COM makes no warranties, endorses no vendor, and has not independently corroborated these notes. Caveat emptor.
Cylinders
Capacity, pressure, dimensions and buoyancy for cylinders commonly seen in cave configurations. Reproduced from the original CAVEDIVER.COM tank tables.
Aluminium cylinders made from 6351-T6 alloy — the alloy used in older Luxfer and other aluminium tanks — are subject to sustained-load cracking in the neck and shoulder. The US Department of Transportation requires a specific inspection regime for them, and Luxfer's own policy calls for visual inspection at least every 2.5 years by a trained inspector, including eddy-current testing of the neck threads with a Visual Plus, Visual Eddy or equivalent device. An ordinary visual will not reliably find these cracks.
Check the markings on any older aluminium cylinder before you fill it, and see Luxfer's guidance and DAN's assessment. This requirement did not exist when the table below was compiled.
| Manufacturer | Material | ft³ | Service PSI | PSI per ft³ | OD in | Length in | Weight lb | Buoy. full | Buoy. empty |
|---|---|---|---|---|---|---|---|---|---|
| Luxfer | Aluminium | 77.4 | 3000 | 38.75 | 7.25 | 26.1 | 26.9 | −1.6 | +4.1 |
| OMS | Steel | 85 | 2400 | 28.23 | 7.00 | 26.0 | 31.0 | −6.7 | neutral |
| Faber / ScubaPro | Steel | 95.1 | 2640 | 27.76 | 8.02 | 23.8 | 37.6 | −8.5 | −1.2 |
| OMS | Steel | 98 | 2400 | 24.48 | 8.00 | 24.0 | 38.0 | −7.7 | neutral |
| Luxfer | Aluminium | 98.8 | 3300 | 33.40 | 8.00 | 26.2 | 40.2 | −3.3 | +3.5 |
| Pressed Steel | Steel | 100.1 | 3500 | 34.96 | 7.25 | 23.9 | 33.0 | −7.5 | neutral |
| Pressed Steel | Steel | 104 | 2400 | 23.07 | 8.00 | 26.2 | 46.0 | −5.3 | −2.5 |
| OMS | Steel | 112 | 2400 | 21.42 | 8.00 | 26.0 | 41.0 | −8.0 | −1.0 |
| Pressed Steel | Steel | 120 | 3500 | 29.16 | 7.25 | 27.9 | 38.0 | −10.0 | +1.0 |
| Pressed Steel | Steel | 120 | 2400 | 20.00 | 8.00 | 29.4 | 52.0 | −7.0 | −2.0 |
| Heiser / Beuchat | Steel | 120 | 3190 | 26.58 | 8.03 | 25.8 | 55.0 | −26.4 ? | −17.82 ? |
| OMS | Steel | 125 | 2400 | 21.12 | 3.00 ? | 29.0 | 45.0 | −9.5 | neutral |
| OMS | Steel | 131 | 2400 | 18.32 | 8.00 | 30.7 | 47.0 | +10.3 ? | +0.75 |
| Heiser / Beuchat | Steel | 140 | 3190 | 22.78 | 8.03 | 29.9 | 63.0 | −28.4 ? | −18.04 ? |
| Heiser / Beuchat | Steel | 190 | 4400 | 23.15 | 8.03 | 31.3 | 87.0 | −62.3 ? | −46.86 ? |
Entries marked ? are reproduced as they appeared in the source but look wrong — a steel cylinder cannot be positively buoyant when full, and a 3.00 in outside diameter on a 125 ft³ cylinder is not physically possible. Flagged rather than silently corrected. A fuller manufacturer-by-manufacturer table also exists in the original material — see the archive.
Pressed Steel Tank (PST) built the high-pressure 3500 psi steel cylinders listed above from the late 1980s until the early 2000s, and has since left the scuba business. Worthington, the other well-known American steel manufacturer, has also stopped producing scuba cylinders.
Both companies' tanks remain in wide service and continue to pass hydrostatic testing — they are sought after precisely because nobody makes them any more. Their DOT special permits have been renewed by successor owners, so the cylinders stay legal to fill; there is simply no longer a factory to buy a new one from.
Faber, Luxfer and OMS-badged cylinders are still available new. If you are buying second-hand PST or Worthington steel, the cylinder's test history matters more than its age.
Equipment
The original resource index carried seventeen headings behind a frameset. They are reorganised here into a single page, with the era of each note made plain.
The original site carried extensive notes on sealed lead-acid packs, charging regimes and home-built burn kits — the state of the art when HID was new and lithium was not an option.
Retained in the archive for historical interest. Lighting has moved entirely to LED and lithium chemistry since; do not build a battery pack from 2002 guidance.
In the United States, scuba cylinders require hydrostatic retesting every five years under DOT rules. An annual visual inspection is not federal law but is universal industry practice — effectively no shop will fill a cylinder without a current VIP sticker.
Older 6351-T6 aluminium cylinders carry the additional eddy-current requirement described above, on a 2.5-year cycle.
Most dive stores will accept cylinders, send them out for hydro, perform the visual and return them filled, passing on the test cost plus a handling charge. For a single cylinder that is usually simpler than dealing with a test facility directly.
Cave diving is hard on regulators — cold water, high flow rates, and long immersions. Service intervals matter more here than in warm open water, and free-flow behaviour in an overhead is a gas-supply emergency rather than a nuisance.
Blended gas is standard practice for cave work at depth. Fills require a facility equipped for oxygen service and a blender qualified for the mixes involved, plus analysis of every cylinder by the diver before the dive.
Diver propulsion vehicles extend range dramatically and change gas planning entirely — a failed scooter means swimming out on a plan that assumed you would not have to.
The original pages covered Gavin, Mako and Silent Submersion units, including a Delrin prop-pitch adjustment screw sold locally.
Texas and Florida cave systems run cold and constant year-round, and cave dives are long. Thermal protection is a safety consideration, not a comfort one — a cold diver makes poor decisions well before they stop functioning.
Cylinders mounted at the diver's sides rather than on the back, for restrictions a back-mounted set will not pass. The original notes date from 2001–2003, when the technique was still comparatively unusual outside sump diving.
Sidemount practice has developed substantially since. Current training is the right source here.
Housing notes from the era of the Canon Optura and the Nikonos, contributed by divers shooting in Texas systems.