Return to equipment page Single cylinder diving is intended only for dives where there is no decompression planned, no solo diving and no penetration of overhead environments. Unless all three of these conditions are true then use a twinset/doubles for the dive.

The same backplate and harness are used, but with a smaller wing. The backplate has a single tank adapter fitted and the single tank is strapped to this. All d-rings, etc., are in the same place, and the harness is still one continuous piece of webbing. Again choose a backplate best suited to overall weighting including cylinder and suit buoyancy. If the single tank has a dual outlet valve, e.g. H or Y valve, then the regulators for a manifold may be used without alteration, except for long-hose length (see below). If a standard single outlet valve is used then the regulator is rigged as follows: The long hose should be 1.5m only as there is no battery pack to hold the excess in place and there will be no penetration of overhead environments. If a battery pack is worn then the standard length hose may be used, alternatively, the excess can be stuffed in the waist belt or looped under the knife/cutters sheath. Run the hose as before and breathe the long hose regulator.

Pony Bottles - Holy Grail or a Comfort Blanket? Pony bottles are worthless, do not use them. If you need a pony then you actually need a twinset. If you cannot see that for yourself then you need more experience or training. Many divers think ponies are a holy talisman: they can commit the sloppiest diving practice violations imaginable and justify it by saying: "but I have a pony!". A stressed diver will be lucky to make it to the surface on one. Usually, the regulators are terrible or the bottle is half empty. Almost all situations where a pony will save a diver could be avoided by better discipline and practices. DO NOT USE THEM EVER!

The short hose should be even shorter or a large loop will flap "in the breeze" as you swim. Rig in neck loop as before. Second stage hoses feed from the right side of the regulator. The wing inflator should come from the left side, and it and the corrugated hose are held in a bungee loop as before. Drysuit feed, if used, should feed from the left also. The HP gauge is clipped to the waist belt d-ring as normal. A dive computer may be used as no decompression is to be done. Back-up lights if needed are rigged on the shoulder straps as before. Whether or not a dual outlet valve should be used is a long-running argument. It does give additional redundancy and provides a continuity between double and single cylinder diving. In reality though, few rental centres will have single tanks with H or Y valves. Single tanks should only be used for recreational diving within the no decompression limits and no cave or wreck penetration, so adequate redundancy can come from sticking with your dive partner. It could be argued that if you need an H valve then you actually need a twinset. If I was diving with my own single cylinders then I would say buy H-valves, but if I mainly used rented singles then I would stick with the single outlet, single regulator rig. A pony bottle, inverted or otherwise, should never be used. They cause drag, they are an entanglement risk, you cannot reach them, they encourage sloppy dive practices and in reality are of little value. A skilled diver can dive safely without one. If you think you need a pony then what you actually need is a twinset. If you don't think you need a pony then just don't take it.