Pony Bottle Valve on of off

[XJae]

i dive with mine [al40] charged and closed.

charged for the obvious reason that i don't want salt water in my 1st stage
and closed for some of the reasons mentioned above but also so i am use to
it that way for when i start using multiple bottles. the theory there is that
when diving multiple bottles with different mod's and you deploy a reg and
turn on a valve there is little chance of breathing off the wrong bottle cause
all the others are closed. i.e. you wouldn't want to accidentally be breathing
o2 at your first stop. that would hold true for an oog diver who grabs your
stage reg as well.

 

[divad]

Charged and off works fine. I practice frequently and there is a always a breath in the hose.

 

[drbill]

I spend a lot of time at or near the bottom filming. I leave my pony reg pressured with the valve off.

One reason is that the purge button can make contact with the rocks, etc., and release a quantity of air from my 13 cu ft pony. My way if it does, I simply recharge the line and turn it off.

Second reason is that I have a slight leak probably due to electrolysis (I dive with steel main tanks and an Al pony). Keeping it off with the valve in easy reach (pony upside-down) helps me retain air.

 

[7ftDiver]

Second reason is that I have a slight leak probably due to electrolysis (I dive with steel main tanks and an Al pony). Keeping it off with the valve in easy reach (pony upside-down) helps me retain air.

drbill could you please explain this electrolysis thing, why would that cause a leak? i too idive a steel main and an al pony and am curious as to why this might happen.

 

[Mark Vlahos]

In the specific case here I make a distinction between a diver that is trained in the use of a stage or deco bottle and a pony bottle. True 7ftDiver is planning on carrying the bottle slung like a stage bottle, but to my knolwedge he has no training on the use of a stage or deco bottle. Using a stage bottle certainly is not rocket science but it involves increased awareness of how depth effects a charged but turned off bottle as the diver moves through the water.

For this specific situation since the pony is to be used as an additional backup and never as a primary gas source and presumably the diver will continue to have an octo connected to his back gas, go ahead and leave it on for the entire dive. If it should freeflow and drain the tank completely you will be in the exact same position as a normal diver who is not using a pony. You will keep adequate gas reserves in the tank on your back and have an octo to donate to an out of air diver. If the valve is open you run the risk of the tank draining, but you will be keeping an eye on the tank to prevent this. If you should need the air, just grab the second stage and use it.

If you do understand what effects differing water pressure has on a charged but turned off regulator then you will probably switch to turning the valve off for the dive, charging the reg as necessary. Just remember that either way should not kill you since the pony is a BACKUP and not a primary gas source. A stage or deco bottle is a PRIMARY gas source that will be used at some point in that dive.

Keep the pony rigged close and keep the hose tidy, you will now have a big thing hanging from your BC in front of you, it will try to get tangled on pretty much everything you get near. On giant stride entrys hold on to the tank to keep it from whacking you in the chin.

Mark Vlahos

 

[ScubaSarus]

DrBill got some explaining to do ther guy . Could it be the 2cnd stage reg isn't adjusted to the IP of the 1st stage?. But I'm eager to learn the electrolysis theory wether others think its viable or not.

 

[XJae]

dr.bill must be talking about how when you put two different metals together one tends to corrode faster. this is especially noticable between aluminum and steel. of course i don't think this would happen with a painted al tank and a galvanized or painted steel tank. it would probably happen with a paint chipped aluminum stage and stainless steel hose clamps though.

i had a chevy truck once that had a steel oil pan with aluminum rivets. some said it was designed that way to corrode the pan within 10 years. go figure.

 

[itemize]

I had many successful dives with an AL30 back mounted pony. The key was making sure the bottle was mounted as close to your back as possible. If the bottle is away from your back it throws the center of gravity off and makes the rig tippy. With the back mounting I kept the gas on throughout the dive.

In hindsight I'd have gone straight to doubles for my redundant gas.

 

[Daryl Morse]

When I dive with a "pony bottle", it's a 40 cf cylinder in a sling configuration, clipped to the left side d-rings of my bp harness (valve up). If it contains nitrox, I have the MOD clearly marked on both sides of the cylinder. When I'm not using it, the second stage is bungied to the cylinder on the outside of the harness. Before I dive, I pressurize the system and then turn off the valve until just before I deploy it. I prefer that way, because it prevents a free flow in the off-chance that the second stage gets bumped.

I don't carry a sling bottle solely as a source of redundant gas, although it also serves that purpose. When I dive with a sling bottle, it's because I intend to use the gas. Sometimes I have air in it, but it could have up to 50%, which may not be breathable at depth. In a situation where another diver was OOA, I would donate whatever reg was in my mouth (either the sling bottle or my 7' primary) and revert to my bungied secondary. In a situation where I was OOA, my primary backup would be my buddy. Depending on what gas was in the sling bottle, I might revert to it as a secondary backup. If necessary, I could open the valve and deploy the second stage quickly enough so I see no advantage to diving with the valve turned on.

 

[lamont]

No spare hand to turn things off is why you would have it on -- it's ready to go, you don't have to have a free hand to crank it open. Simultaneous freeflow on primary and pony, and enmeshed in a net, is starting to get to the "really bad day" zone. For an off pony to be a plus you would have to postulate the freeflow, no hands free, but that one hand became free when the pony was needed.

What you have to postulate for having it off is that you never need the pony *immediately*. That means that you have a gas plan and adequate situational awareness so that you aren't going to go OOA without any warning. You are also going to respond to your buddy going OOA by donating from your backgas and not the pony. If these conditions are true, the pony never needs to be deployed immediately, which means that you have time to free up a hand to open it up.

Since there is no reason for it to be open all the time, you should turn it off because of the risk of a free-flow when you've got your hands full.