Redundancy and H / Y valves

[fisherdvm]

I read a post by Dr. Bill concerning failure of an H valve, and why he prefers a pony. But from a redundancy and safety standpoint, it seems like an H/Y valve with 2 first stages is better than 1, especially for very cold water diving right?

Why don't we hear it pushed more in the recreational side? It seems like it can prevent free flow incidences that might have cause the death of some cold water divers. Going to double seems excessive.

I know someone asked this before, why don't someone make an H or Y valve adapter that can convert a regular single yoke/DIN set up into two valves? Of course, the extra connection is a new point for failure....

I tried to do a search on this, but of course, if it is less than 3 letters, they wouldn't let you search the topic.

 

[SteveAD]

An H or Y valve for redundancy in extreme cold conditions is not nearly as effective as a pony.

1. with 2 outlets on a single tank any freeflow will serious compromise not only the delivery system, but the whole gas supply.

2. The valve(s) on a single tank will be harder to reach/take longer to close that those on a set of doubles exacerbating point 1.

3. The initial free flow will drop the gas temp in the (only) tank increasing the likelyhood that the first breath from the secondary reg will result in an immediate freeflow.

There is a reason why H and Y valves are not seen very often. They simply don't do a very good job at what they are supposed to do. The expensive part of putting together a pony setup is the reg. The cost difference between a funky valve and a pony tank is most likely less that $100. If you want redundancy go all the way.

 

[drbill]

I don't dive really cold water (48 F has been my limit so far) so freeflows from cold water are not my concern. I have had tank valves themselves clog as often as regs failing so an H- or Y-valve is of no use in such a situation. A truly redundant system is the only "insurance" I feel comfortable with (I actually dive with FOUR second stages!). I'm now (finally) diving with redundant computers (so far just 2 or 3).

I just wish I could figure out how to dive with redundant brains (other than buddying up)... maybe two would make mine equal to a single fully functioning human brain!

 

[ClayJar]

I have had tank valves themselves clog as often as regs failing so an H- or Y-valve is of no use in such a situation.

Actually, the Y-valves I've seen have all been redundant all the way through (except the threads and neck O-ring). They have two dip tubes and independent air paths all the way through.

The H-valves I've seen were *not* redundant all the way through, but the Y-valves were.

 

[fisherdvm]

Seems like, with the valves set off at least 4 inches apart, we do have a large enough heat sink to prevent one first stage from freezing the second first stage. I can not see how the temp could drop in the tank too rapidly, that it would increase the likelyhood of the second valve/first stage to free flow also if the first were to free flow.

Being a minimalist, I would feel that the initial investment in a $150 Y valve might be worth the price without dragging along a pony. But then, if you dove from a boat that provided the tanks, a pony is still the answer to redundancy.

 

[drbill]

Actually, the Y-valves I've seen have all been redundant all the way through (except the threads and neck O-ring). They have two dip tubes and independent air paths all the way through.

I didn't know that. In light of that new information, I take back all the nasty things I've said about Y-valves in the past!

 

[texdiveguy]

I dive an H-valve and carry a pony bottle when recreational diving my single hp130....so I have it covered from both angles.

 

[shoredivr]

2. The valve(s) on a single tank will be harder to reach/take longer to close that those on a set of doubles exacerbating point 1.

My single steel tanks have DIN h-valves. I haven't noticed any time difference in valve drills or difficulty in reaching valves compared to doing the same thing in my doubles.

I have a similar set-up to Texdiveguy, except they're 108s not 130s

 

[SteveAD]

My single steel tanks have DIN h-valves. I haven't noticed any time difference in valve drills or difficulty in reaching valves compared to doing the same thing in my doubles.

I have a similar set-up to Texdiveguy, except they're 108s not 130s

I am an individual of somewhat less than average flexibility. While I can reach all vave knobs while wearing doubles, I am hard pressed to reach the knob on a single unless the tank is mounted so high I am at continuous risk of a concussion.

 

[Sam Miller III]

I am an individual of somewhat less than average flexibility. While I can reach all vave knobs while wearing doubles, I am hard pressed to reach the knob on a single unless the tank is mounted high....

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Don't Worry.Miller's Law of low air comes in to effect..If you are running low on air your arm will automaticlly grow at least six inches so you can reach the knob...You can quote me on that!

sdm