Pony vs. H-Valve

[Spectre]

Lemonade once bubbled...
What is the minimal size that is generally considered sufficient for a pony bottle? 13+? 19+? 30+?

First you have to ask what you will use it for. NDL dives within recreational limits? If that's the case, then you need to sit down with your 'at stress' SAC rate, and calculate how much air you would need to make a normal ascent from 130 fsw, with a safety stop, with your obvious fudge factors built in.

If you have dreams and aspirations to go beyond recreational limits in depth or deco, you'd probably be better off looking at a 30 or 40, that you can convert to a deco bottle in your future.

Of course, it all depends on your needs and your future plans.

 

[JDostal]

Part of the reason for a pony bottle is an emergency air supply in case you make a mistake and run out of air in your main tank. Doesn't matter how many regs and valves you have hooked to one tank, when it's empty, it's empty

 

[JimC]

Omicron once bubbled...
Part of the reason for a pony bottle is an emergency air supply in case you make a mistake and run out of air in your main tank. Doesn't matter how many regs and valves you have hooked to one tank, when it's empty, it's empty

Planing
Buddy
Bigger tank

Running out of gas is avodable.

 

[JDostal]

Yes, it is avoidable. Heck, just watch your gauges close enough and stick to the plan and you should know when to surface. However....it is still nice to have a backup just in case.

I personally don't use one...but can see the logic behind it.

 

[IndyScott]

I use a pony because of the cost..

 

[cavediver]

Lemonade once bubbled...
Why carry a pony tank if you can get an H(Y)-Valve?

Here are my thoughts:

• H-Valve is less expensive than a pony bottle + harness.
• Both provide same redundancy for the first stage.
• More air with pony? Why not get a larger tank? Seems like 120 cf + H-Valve is a less cumbersome setup than a 100 cf + 20 cf pony.

Am I missing something?

I’d like to hear what you guys think, and what other considerations are out there.

Thanks.

you cant shut an H valve down from a tank/valve o-ring failure. H valves are a redundent reg source not a redundent air source.

 

[Rick Murchison]

cavediver once bubbled...
a tank/valve o-ring failure

I assume you're referring to a catastrophic failure of the main o-ring between the tank and the valve.
I've seen a lotta' strange stuff in three+ decades of diving, but that ain't one of 'em.
But you've got me wonderin' now, just how fast you'd lose your gas if such a thing did happen... the gas has to escape around a whole lot of threaded tank/valve interface... reckon I'll run a little experiment & see. And report.
Rick

 

[cavediver]

Rick Murchison once bubbled...

I assume you're referring to a catastrophic failure of the main o-ring between the tank and the valve.
I've seen a lotta' strange stuff in three+ decades of diving, but that ain't one of 'em.
But you've got me wonderin' now, just how fast you'd lose your gas if such a thing did happen... the gas has to escape around a whole lot of threaded tank/valve interface... reckon I'll run a little experiment & see. And report.
Rick

true it is rare. but are you willing to risk being at depth and that happen. you still have to do a stop at 15 not to mention your slow accent and I would hate to find out if that leak with last 3 mins.

 

[JimC]

Unfortunatly a pony dousn't guard your back gas against the MUCH more likely failures of blowing a hose, or regulator failure. I'd rather have the redundancy for all of my gas.

I don't know, and I don't think anyone on this board has ever seen a neck o-ring go. Thats a heck of a lot of bottom time. Besides, whats your boddy for?


The best answer is ofcourse doubles.

 

[MikeS]

Rick Murchison once bubbled...

... the gas has to escape around a whole lot of threaded tank/valve interface... reckon I'll run a little experiment & see. And report.
Rick

Rick,

The Sherwood valves on my HP120 seem to have a pressure rrelief hole, so if the gasket leaks the air would come out there rather than through the threads. I suspect that the hole is there to prevent protective plugs from getting stuck i.e. you put in a Delrin plug and accidentally open the valve. The pressure on the threads would make it difficult to get the plug out.

Mike