Pony bottle/alternate air

[letterboy]

There are a couple of reasons that I say the stage/decompression bottle are more likely to be lost.

The biggest reason is just that they only have a single output valve and a single reg. Especially in cold water, where free flows aren't uncommon, there's just always the chance that the single valve/reg will be what fails. Of course cold water isn't the only thing that causes free flows. There are purly mechanical failures that can cause air to leak out or water to leak in...but depth, even in warm water, results in a much greater demand through the reg...at 33 ft double...66, triple...99 quadruple ect. A reg can freeze even in warm water simply due to the cooling effect of a greater amount of gas expanding within it at depth. The combination of cold and depth is, of course, the worst. I know some divers get to dive warm water but most of the world has some pretty cold water.

Other reasons include the fact that they are clipped on and therefor ditcheable. Something that's ditchable, might get ditched. Also, sometimes (mostly in caves) we actually leave them to be picked up when we need them. They might get dropped (staged) on the way in or even on a previous setup dive. We hope that it's still there and that it works when we get to it but it might not.

Makes sense.

 

[Nemrod]

MikeF says:
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"By contrast, a pony bottle is usually a single tank with a single output valve but it's reserved as the backup. You can see that the whole concept is pretty much backwards from that of a decompression or stage bottle which is backed up. We know that our stages and decompression bottles are the most likely to be damaged or lost and have no redundancy so we have a backup for them."
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But the Pony gas is backed up by the main, using the Rule of Thirds, your dive should have been over and you should be sitting on the boat with 1/3 of your main supply still in the tank--plus--the pony. Therefore--you still have TWO fully independent sources of air with enough capacity to get you home.

The Rule of Thirds---one third in (down, out), one third back (up etc and onto boat or shore) and when your sitting on the boat you still have 1/3 in reserve.

If this sounds conservative--it is---size your main tank to provide for that--an aluminum 80 not enough for your profile??--get a bigger tank. Yes, at some point doubles become required for the dive profile. For me when the profile requires more than 100ish cf then I start thinking doubles.

The pony should be sized to approx 20% to 30% of your main supply--you should not be doing deco or overhead diving with this system. It is intended as a highly redundant system for sport divers--not Tech dives into the bowels of the Oriskany at 190 feet.

N

 

[MikeFerrara]

MikeF says:
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"By contrast, a pony bottle is usually a single tank with a single output valve but it's reserved as the backup. You can see that the whole concept is pretty much backwards from that of a decompression or stage bottle which is backed up. We know that our stages and decompression bottles are the most likely to be damaged or lost and have no redundancy so we have a backup for them."
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But the Pony gas is backed up by the main, using the Rule of Thirds, your dive should have been over and you should be sitting on the boat with 1/3 of your main supply still in the tank--plus--the pony. Therefore--you still have TWO fully independent sources of air with enough capacity to get you home.

The Rule of Thirds---one third in (down, out), one third back (up etc and onto boat or shore) and when your sitting on the boat you still have 1/3 in reserve.

If this sounds conservative--it is---size your main tank to provide for that--an aluminum 80 not enough for your profile??--get a bigger tank. Yes, at some point doubles become required for the dive profile. For me when the profile requires more than 100ish cf then I start thinking doubles.

The pony should be sized to approx 20% to 30% of your main supply--you should not be doing deco or overhead diving with this system. It is intended as a highly redundant system for sport divers--not Tech dives into the bowels of the Oriskany at 190 feet.

N

I saw your similar post in the other thread. I think it's a good discussion of gas management.

No argument with applying the rule of thirds, except that it is overly conservative for some OW situations...for instance a shallow dive where you can ascend anyplace. The objective, of course, is still sound which is to have twice as much gas as you need for the return/ascent accounting for a possibly elevated breathing rate.

The only other comment that I have is that I'll bet you two air fills that if more divers were applying this or any sensible gas planning, we wouldn't have nearly as many pony bottle questions on the board in the first place.

 

[Marvel]

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[DandyDon]

Thanks much Marvel. Should have hit the button a long time ago. Appreciate your good work here...

 

[divemastercpas]

i dive single hp119 whith a 19cf whith first, second stage and a spg, i use it with a diverite stage strap clipped to my right side, it is on before i go down.
i'm a rec diver i use the pony as soon as i dive below 60 feet.

 

[bentex]

Does slinging a pony or carrying a pony on your back affect your balance in any way?

 

[DandyDon]

Yep, I'll move weight to the oppostie side - 2 to 4# more

 

[citykid]

Good info going on here save the kunckleheads who do nothing but bi*ch.

To some who go with the sling method. You state for the ablity to see the SPG. My attitude is to have it always, turned on always, and hope to never need it. If my AAS ran out of air under water for some reason, so what? I wouldn't abort the dive because of that. And if I find I am in need of my AAS, I'm already in trouble. To me it is an extra piece of protection in a very bad situation. An absoulte last resort option. This is when there is no buddy near, or I'm caught up somehow, etc.

I am thinking of attaching it to my Zeagle BC on the back, SPG, 1st & 2nd stage w/ the 2nd slung somewhere in front. This would NOT be an octo for me or a buddie. This is for when I have NO air available. To the people who say if you have good diving diciplin then you should never need an AAS. I practice good diving skills. I believe I am a good buddy when diving. I am very aware of my air supply, time, depth, etc. But as I have learned in life there is always something that can come up that you haven't thought of. Then what do you do 'Mr. I shouln't have any problems'? Mr. Murphy WILL show up. Not all the time, but he does show up. You gotta' be prepared for what you haven't thought of. Here endth the sermon.

 

[DandyDon]

Ok, but on my back where I could not see the valve, leaking first stage or spg is what got me into trouble. Wanta buy a brand new tank mount for one...?