Appeared in DIVER December 2006


British divers seem to be in love with pony bottles. They like to strap them to the side of their main tank so that they have a redundant 3-litre supply of gas for use in an emergency, but this turns an otherwise comfortable single cylinder into an unbalanced and uncomfortable weight on the back.
How does an H-valve help Instead of diving with a 15-litre supply of gas divided into 12 and 3 litres, why not use a 15-litre tank with an H-valve This allows you to designate any part of those 15 litres as your fallback supply should your primary regulator let you down on a dive.
You use it in exactly the same way as a twin-set. Two cross-flow valves are mounted together, each with its own method of opening and closing.
I use mine with the regulator fitted to the left side supplying my BC direct-feed, and a transmitter for my tank-pressure display on my computer. The regulator on the right supplies the direct-feed to my drysuit and a high-pressure hose and conventional contents gauge. I can even fit an octopus rig to either, if I want to.
In this way I get complete redundancy with two totally independent regulators, and always have a method of providing buoyancy if I need it.
In order to fit two regulators without getting headaches from sorting out hose routeings, one side of the H-valve rotates. That said, the only hose I use on the left-side regulator coming over to the right is one to that regulators second stage.
I go in the water with both sides fully turned on. Should my primary go into free-flow, for example, its no great shakes to reach back, or even pull the set over my head and turn it off. An H-valve turns every single cylinder into a twin-set.
But its the same reservoir of gas, I hear you protest.
What if youve run out of air Theres no redundant supply!
Well, I consider my reserve to be the last 50bar (or 3.75 litres at full pressure) of gas in my 15-litre cylinder that started the dive with 200bar. Thats more gas than a pony has. I dont touch it unless I have to.
This does mean watching your contents gauge and managing your air supply. But if you cant do that, theres a good chance youre walking down the hard shoulder of a motorway with your petrol can, having run out of fuel on the way to the dive site!
What if an O-ring blows on your tank during the dive Turn that side off and make your way calmly back to the surface, just as you would with a twin-set.
The Beuchat H-valve is equipped with DIN threaded connections together with an A-clamp adaptor. It costs 69.99. One day, all single tanks will be equipped this way.
  • Alpha Distribution 01709 515157,

  • Divernet
    + Total redundancy
    + No need for a pony cylinder

    - None, unless you insist on separate gas containers