Examples, Stories, Anecdotes of Tank Valve Failures. (Side Topic H-Valve Single Tank Diving)

[tursiops]

I have heard both schools of thought. Shut down isolator to ensure you retain at least half of your gas, then find the offending post. The other school of thought is you are wasting time shutting down the isolator and instead should shut down the primary first stage port you are breathing as it will be the most likely to have failed. All of this of course is assuming you can't identify which post has failed to begin with. Which I would think would be unlikely since one side would be louder than the other and if a second stage begins free flowing it is obvious which posts has failed.

And all this is one of the big reasons I moved to sidemount.

 

[Doby45]

I would say this would be your best bet if you were dead set on a single tank. Totally independent airways.

Here is an interesting concept I have not seen before. Not cheap either at $171.

SAS Valve - Beuchat

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[RyanT]

If you're thinking about this path, why not doubles or side mount?

 

[PfcAJ]

Thanks for the contribution, AJ. I certainly agree I don't think an H valve is suitable for caves. Would you agree in OW the risk is significantly less in the event of one of those types of failures you mentioned since you can obviously get shallower quicker than you can in a cave and be able to make a gas switch sooner? In other words, where do you put the H valve on your risk tolerance level (setting cave/penetration/big pinnacle dives aside).

I guess I’d start with asking if there’s enough volume in a single tank to provide enough gas for the dive plus reserve.

al80s hold roughly the same as a juiced up lp120.

so I guess if your talking about using an lp120 filled to 3600psi then it’s maybe ok.

I think it’s a one-trick pony though. Personally, I’d rather take al80 doubles and keep it consistent.

 

[johndiver999]

I have heard both schools of thought. Shut down isolator to ensure you retain at least half of your gas, then find the offending post. The other school of thought is you are wasting time shutting down the isolator and instead should shut down the primary first stage port you are breathing as it will be the most likely to have failed. All of this of course is assuming you can't identify which post has failed to begin with. Which I would think would be unlikely since one side would be louder than the other and if a second stage begins free flowing it is obvious which posts has failed.

I am somewhat skeptical that you will be able to identify the side of the leak/failure from simply sound. It seems that the ability to respond quickly and accurately in the shut off procedure is critical to the goal of successfully preserving enough gas to ascend.

Perhaps a more realistic protocol would be to open the waist strap and chest strap and plan to flip the tank over your head immediately so you can see where the failure is? That is a question not something I have ever done.

Perhaps another procedure might be to just shut one side down blindly, and wait 10 seconds to see if that resolves the problem. It should work half the time? but then you need to open a valve and close one. I'm curious to hear what best pratice is on this type of gear - it seems important to me. Plus, the H-valve set up is going to INCREASE (double) your chance of regulator failure, so this has to be considered in the over all decision.

Obviously if the failure is a second stage freeflow etc., then there should be very little ambiguity as to which side to shut down, if you know your gear set up.

 

[PfcAJ]

I am somewhat skeptical that you will be able to identify the side of the leak/failure from simply sound. It seems that the ability to respond quickly and accurately in the shut off procedure is critical to the goal of successfully preserving enough gas to ascend.

Perhaps a more realistic protocol would be to open the waist strap and chest strap and plan to flip the tank over your head immediately so you can see where the failure is? That is a question not something I have ever done.

Perhaps another procedure might be to just shut one side down blindly, and wait 10 seconds to see if that resolves the problem. It should work half the time? but then you need to open a valve and close one. I'm curious to hear what best pratice is on this type of gear - it seems important to me. Plus, the H-valve set up is going to INCREASE (double) your chance of regulator failure, so this has to be considered in the over all decision.

Obviously if the failure is a second stage freeflow etc., then there should be very little ambiguity as to which side to shut down, if you know your gear set up.

It’s actually pretty easy to figure out what side the leak is on. In all but the tiniest of leaks you can tell. Super easy to identify IP-caused leaks, too.

Woe unto thee who tries to flip his tanks over his head wearing a drysuit. Or multiple bottles. Or a scooter.

 

[johndiver999]

I dont get the impression the op is using a scooter or dry suit, but if you say you can tell which side on an h-valve - then I have to believe you since I have never has that situation. The regulators are 3 inches apart... you can tell instantly by the sound on the first stages?

 

[CuzzA]

If you're thinking about this path, why not doubles or side mount?

Spearfishing would eliminate side mount and manifolded doubles aren't practical on small private boats, IMO. It could certainly be done, but would be a real PITA, especially in anything but flat calm seas.

 

[CuzzA]

I dont get the impression the op is using a scooter or dry suit, but if you say you can tell which side on an h-valve - then I have to believe you since I have never has that situation. The regulators are 3 inches apart... you can tell instantly by the sound on the first stages?

Right, no drysuit or scooter.

I think you make a good point about identifying the offending reg from a catastrophic loss of gas with an H valve. Perhaps a more practical approach would be just dive a single jacked up steel and tank mount AL 40's on either side. One being the redundant bottom gas and the other being deco gas. Of course gas planning will need to be done right to make sure you have the gas to complete the dive considering all of the different types of gas failures.

I found this photo from SpearBoard. The removable 40's seem to makes this a much more practical setup for small vessels.

 

[johndiver999]

Well that rig looks to require 4 independent regulators - all back mounted. I guess your idea would be to drop the H-valve aspect?