DIR and PONY's

[MikeFerrara]

Genesis once bubbled...
is the potential for a burst-disc failure. While a tank neck O-ring can fail too, the gas escape rate is limited by the threads around the valve if it happens, and its more likely to be a leak than an explosively rapid gas loss.

A burst disk failure underwater could be very bad, but I don't know how common that possibility is. I have seen them fail while a tank was being filled, and at nowhere near maximum pressure, at one of the LDSs in the area.

Yes it isn't as robust as an isolated manifold but when I need doubles I use doubles. The most common failure is a reg/hose failure and an H-valve covers you for that.

I have never seen or heard of a tank nech O-rinf failing. I have seen burst discs go in the water but it was on over filled steel tanks. If the valve is maintained and the tank not overfilled it's pretty rare. I have seen yolk o-rings go a bunch of times and I don't use them for the most part.

 

[Big Bubbles]

Who cares what DIR says if you want to use a pony then use one this should be personal preference although I agree with Mike if you think you need extra gas dive doubles.