Pony Bottle, On or Off

Here is one I expect to hear different opinions on...

I'd like if possible to hear from experienced divers and Instructors on this one.

Question for Instructors:
When you teach using a redundant air source, do you teach students to turn it on prior to entering the water... or that they should leave it off and turn it on only when ready to use (if necessary?)

For Experienced Divers... Especially SOLO divers:
Do you turn your pony bottle on prior to entering the water or do you leave it off and positioned where it will be easy to turn on in the event use becomes necessary?

On the surface the logical choice would seem to turn it on and have it working upon entering the water... however I've heard stories and believe it entirely possible to be true... that the regulator attached to the pony may have a slight free flow which could leave the bottle empty unknowingly... and in a true emergency, an empty pony bottle could spell a much biger disaster than one you had to turn on.

What are the thoughts and what is being practiced out there in the real world? Thanks for your answers...

Off.

...............

On to charge before entering the water then back on and off 1/4 way thru the dive, again at 1/2, and then again at beginning of ascent at which point it stays on. Reason for this is it does offer some insurance against water pressure migrating back thru the hose ( very minor issue), and if the reg would get bumped or freeflow all the air you'd lose is what's in the hose. On the other hand should you need to deploy in an emergency there is a breath or two while you are turning the valve on. And it builds muscle memory for working the valve. Don't need to see it to use it. My tech instructor teaches on then off, on at the turn point then back off, and on as we start ascent and left on til surface. This is of course with the bottle slung. I would not carry one any other way. I have a 19, 40, and if need be an al80 I can set up.

When I solo dive I sling an AL40. I pressurize the bottle and turn the valve off.

If you are slinging a pony, this is a practical alternative ... although you can keep it pressurized as long as you do a bubble check to make sure there are no leaks in the reg connections.

If you are back-mounting, you will want your bottle turned on prior to descending, since most back-mount systems won't really give you the option of reaching your valve (not easily, anyway).

... Bob (Grateful Diver)

I sling a 30 or a 40. On until the bubble check is done and then off but leaving the hose/reg pressurized. I also make it a habit to look at the spg on the slung bottle periodically to verify not losing air. I also do a swap to the slung bottle reg and stow my primary once or twice a dive just to make it a natural movement. If you actually need it, that's not the time to be figuring out how to unstow the dang reg.

On. Too hard to reach when attached to the tank. But once I had that exact thing happen. My pony reg must've had a leak. The pony was empty after the dive. The technician said since I hadn't used the pony in a long while something in the reg went amiss, a problem that can and does happen (relatively new reg). Guess I'll still leave it on and make sure the reg is OK--just can't reach it otherwise.

TMHeimer:

On. Too hard to reach when attached to the tank. But once I had that exact thing happen. My pony reg must've had a leak. The pony was empty after the dive. The technician said since I hadn't used the pony in a long while something in the reg went amiss, a problem that can and does happen (relatively new reg). Guess I'll still leave it on and make sure the reg is OK--just can't reach it otherwise.

Click to expand...

Follow-up... If you placed it where you could reach it... would you leave it on or off?

This is written from the perspective of a warm water recreational solo diver: My philosophy is to make using the pony a regular part of my diving, making its use easy and unobtrusive, and having a system that I can travel with and use without complication on commercial dive boats. I use a 6 cu.ft. pony attached to the s.s. plate (with velcro straps for argon dry suit bottle) and pony is turned on before the dive. I carry a pressure gauge and test before each use. The second stage is held to the d-ring on my right waist belt where a free flow would be visible. I realize gas supply is minimal and safety stop might be abbreviated but my objective is to arrive alive. I have had a larger bottle but it tends to sit on my office floor. I actually use this set-up, I travel with it, I practice its deployment, and I barely notice that it's there. I know this system would be nearly useless in an overhead environment or cold, dark water where breathing rate is likely to be elevated. For open, warm water it has been a good option for me. Never had to use it by the way, other than practice.

I sling it. I pressurize it and turn it off, once I start on my way down I turn it on and then turn it back off at my safety stop.

Solo diver. Pressurized and off. Monitor the SPG on the slung tank to maintain pressure.