Running your BCD / Dry suit off your Pony?

[shadragon]

Has anyone ever seen or used a BCD or dry suit hose attached to a Pony bottle reg instead of the main tank?

I know the Pony is designated for Emergency use, but I have seen people use Pony bottles to inflate lift bags so the logic is the same.

If a BCD or dry suit uses 200-500 PSI of air (complete guess, I have no idea how much gas is used during an average rec dive for them - do you?) then running it off the Pony would give you more air in your main bottle to breathe. When you use air in your BC or dry suit you are effectively wasting good breathable air as it gets dumped on ascent. It is a bigger waste if it is more expensive NITROX gas. 99% of the time the pony is not used unless there is an emergency. Overall gas consumption would be the same, but you would have more gas to breathe from your main bottle. Yes, 200-500 PSI is not a huge difference (assuming those numbers are correct, again that is a guesstimate), but that is a safety stop or a few more minutes of down time to comfortably deal with a situation. Assuming a low amount of air used for the BC or dry suit from the Pony there should still be an ample reserve in the Pony to get you to the surface if needed.

 

[D_B]

I'm a novice, and never dived with a pony, but that thinking sounds like a slippery slope to me ... your pony is not to be used, unless needed

OK, your asking if anyone has seen someone do this .... I should not have piped in

 

[Darin]

Shadragon-

I don't know if i've ever seen anyone run a BC or drysuit on a pony bottle, per se...

Many DS divers will run an argon bottle for DS inflation, NOT breathing air. It has much better insulating properties than air. Maybe that's adding some confusion...

I do run my DS off my back gas. I don't mind the few hundred psi worth of air used during a dive. However, on deep, dives, that air goes quick so....

I agree with you, doesn't make much sense to run a BC on a pony bottle. Either A) just use argon, or B) don't worry about it. I use very little air in my BC anyway.

I'm sure you'll get many more posts making more sense than me.

Darin

 

[Scared Silly]

It is common for divers diving dry to use a dedicated bottle for dry suit inflation. Often filled with Argon which is NOT breathable. The merits of when to use argon seem to be an open question. Typically with a 6cuft bottle @ 3000 psi you can get around 3 or so dives out of it.

As using gas out of a pony bottle think of it this way 3-6 cuft out of a 80-100 cuft cylinder is not going to make or break a dive. 3-6 cuft out of a - 13-19cuft may make or break a pony usefullness when you really need it.

 

[Web Monkey]

Has anyone ever seen or used a BCD or dry suit hose attached to a Pony bottle reg instead of the main tank?

It's a bad idea for a number of reasons, not the least of which is that a typical pony only contains enough air for a safe ascent (if you're lucky).

Using it's air to extend your bottom time (which is what you're attempting to do by saving your main tank air for breathing) leaves an unknown amount in the pony, which adds a ton of unknown risks. At that point, you don't know if it contains enough air to get you to the surface (or any air at all for that matter).

It also gives you extra hoses that don't route properly and the very real possibility that you will hit your BC inflator and find that nothing happens.

A pony is for when you screw up and run OOA and can't find (or don't trust) your buddy. If you start using it as a general purpose air source, you can no longer trust the gas calculations you used when you first sized the bottle, so you would be diving with a false (falser?) sense of security than if you had a known full pony.

Terry

 

[ClayJar]

Well, you could dive using the pony for inflation, however, that adds a few issues that must be considered:

• You must work out a more involved gas plan: At any given depth, how much air will you need in the pony for your exit strategy, including problem resolution time prior to ascent?
• Is your pony sized such that the gas plan is workable at the depth to which you're diving?
• Obviously, your pony must have a "real" SPG able to be easily monitored. You need to monitor the pressure to be certain you stay on the plan and do not break into your exit air.
• What strategy will you use if you're on the dive and you run up against the limit of air able to be sacrificed for inflation? Will you end the dive? Will you switch hoses to connect your back gas for inflation?
• Will the additional task loading and skills required for all this be too burdensome?
• Are you comfortable trading that amount of emergency-handling air time for however much back gas time you'll get out of it?

Personally, my pony isn't large enough that I would use it as an inflation source, too, but if I had a 30 or 40, I might think about it. I don't know that I'd ever actually go that far.

As I do have a full SPG on my pony, however, you bring up an interesting idea. One of these times, when I'm diving with one of my implicitly-trusted buddies, I'm going to have to add an LP inflator hose to my pony so I can see precisely how much air I use for drysuit inflation on a typical drysuit dive. Knowing the amount of air I used and the computer-logged dive profile, I'll be able to better understand and plan around how much air a given drysuit dive will use for suit inflation. (It wouldn't be a problem using the pony as merely an inflation bottle for a dive with them, as I can certainly count on them as my redundancy. I don't think I'd do the experiment on a solo dive.)

 

[MSilvia]

Of course, if the "pony" is dedicated to suit inflation (with air, argon, etc) and doesn't have a second stage for breathing, then the gas planning isn't relevant... so long as it doesn't mean you're going without a redundant breathing gas when you need one.

In other words, an ADDITIONAL small tank used for just for inflation may not be a bad idea.

 

[shadragon]

As I do have a full SPG on my pony, however, you bring up an interesting idea. One of these times, when I'm diving with one of my implicitly-trusted buddies, I'm going to have to add an LP inflator hose to my pony so I can see precisely how much air I use for drysuit inflation on a typical drysuit dive. Knowing the amount of air I used and the computer-logged dive profile, I'll be able to better understand and plan around how much air a given drysuit dive will use for suit inflation. (It wouldn't be a problem using the pony as merely an inflation bottle for a dive with them, as I can certainly count on them as my redundancy. I don't think I'd do the experiment on a solo dive.)

One neat thing I did see was a HP hose with a micro pressure gauge (size of a dime) in the end of the hose. Lets you see the Pony pressure without having to have a regular size SPG. This picture is a little bigger than the actual unit:

 

[FoSheZZie23]

If you do intend to use your pony as an inflation bottle i wouldnt recommend going on any dives that you "NEED A PONY" for me that number is below 60 feet. Its just a reasurance factor for me, i like the feeling of having a full pony bottle that if someothing happens I will have the whole thing. The extra hoses wouldnt be very comfortable either. In my opinion I wouldnt use my pony as an inflation bottle unless i was running a 30cu pony.

 

[loosebits]

I wouldn't think it would be worth the effort. A 35# lift BC is around .5 cuft in volume full inflated (if my in-my-head calcs are right). If your RMV is around .5 CFM then fully inflating your BC at any depth only takes 1 min off of your dive time at that depth. I can't imagine that even with the worst saw-tooth profile (where a lot of BC inflation/deflation is used) would you use much more than 3 mins of breathing gas. Hardly seems worth the effort of bringing a dedicated pony.

If you are really concerned about air loss due to BC inflation, perhaps a simpler (and just as effective) solution would be to orally inflate.