What the heck is a H valve?

[texdiveguy]

I've recently decided I'd like to start diving with a redundant air source. I always thought that meant 2 options: pony or doubles. Someone suggested that I could use an H valve instead.

-- If you are diving a single and have no need for the additional gas that doubles can provide, nothing wrong with that,,a 19cf pony bottle is a great pick,,,,adds another source of emg. gas and is very easy to manage.

[/QUOTE]So - what the heck is an H valve & what does it buy me? Is it a good alternative?[/QUOTE]-- I answered this part above in my previous post---H's are a good thing in the right application.

 

[TheRedHead]

I'm leaning towards a pony simply b/c I don't think an H valve is enough and I'm not so sure I'm ready for doubles. I need to learn more.

I would get a 40 cu ft pony. If you are going to sling a pony, take enough air that you can do all your planned stops with a wide margin of error.

 

[BIGSAGE136]

An uncontrollable freeflow at 120' with deco obligations is nothing to take lightly. I dive with some of the BEST buddies on the planet. Why burden the dive? IF you find yourself in a solo situation, and many people do they just dont admit it. What is YOUR backup plan.

This is going to vary widely for individuals. My take is make your self comfortable in the water, know what the hell you are doing, and be prepared to save your own arse.

 

[TheRedHead]

An uncontrollable freeflow at 120'.

The H valve would solve that problem. Not that I'm advocating solo diving, but the scenario of the 120' freeflow is the reason do dive an H valve.

 

[BIGSAGE136]

Add to that.... your pony contains 50% for that SWEET deco....You cant touch it until you hit 60' MINIMUM or you die. The last footage will be argued forever but personally
I wont sip until 55'.

 

[TheRedHead]

Add to that.... your pony contains 50% for that SWEET deco....You cant touch it until you hit 60' MINIMUM or you die. The last footage will be argued forever but personally
I wont sip until 55'.

I use 1.6 for deco gas so the mod is 72 feet. Call it 70 feet. He needs enough gas to get to 70 feet or in your case, 60.

 

[texdiveguy]

Matt.... I have seen some very interesting answers to your questions. I assume you are doing recreational profile NDL diving from the content of your questions. If you are comfortable with your current single gear configuration,,,,then just add a simple pony set-up as a margin of safety only,,not as an extension to your bottom gas. A 40cf bottle is a bit over kill for recreational diving were you simply have a 'deep' stop if needed and a safety stop.....a 19cf bottle is plenty of gas to manage most encountered emg. situations. The use of a slung pony is only for emg. and that is it! Remember that proper dive planning in terms of dive profile and basic gas managment is the key to safe runs.....there is no excuse for OOA situations short of catasrophic eqpt. failure which are very rare as long as you are caring and checking your gear on a regular basis. Dive conservative with appropriate back-up and enjoy!!

 

[BIGSAGE136]

Put that pony at 21% if YOU dont understand the previous posts.

 

[Thalassamania]

This is where the logic escapes me. I don't say this to start flames or troll, but out of genuine interest in the logic of the situation/solution.

We assume your diving a BIG tank at 120 and are carrying a stage or pony of 50/50.

Your regulator starts to freeflow wildly. Your buddy is no where to be found. You can't (or won’t, doesn't matter for the sake of this discussion) use your 50/50 till you get up to 55 feet.

We all on the same page? Good!

Let us also assume that holding your breath of a two minutes is a normal skill and for one minute a trivial proposition.

Why not:

1) breathe off the freeflowing regulator to 55 and switch to 50/50? or

2) make a free ascent to 55 and go on to your 50/50?

Breathing off a freeflowing regulator is not that big a deal.

Making a free ascent from 120 to 55 should be perfectly safe to 60/min and will only take a over a minute. I say that rate is ok, because dP/dT is actually less that dP/dT from 30 to the surface at 300 FPM.

For me, it once again comes down to a minimalist approach; less gear is better, as long as there's a rationale solution. To buy the farm because of said freeflow would require:

1) No buddy, and
2) Not enough gas to make the freeflowing ascent to 55, and
3) Not being able to hold my breath for 65 seconds.

Perhaps I'm unimaginative, but I really can't foresee a maximum creditable accident that trumps all three of those criteria.

 

[BIGSAGE136]

You answered your own question