Open or closed valve on pony bottle?

[sunnyboy]

If I'm diving a stage as extra gas for the dive and plan on using it, I usually start the dive breathing off the stage, so it's on. Once I've used it up, I switch to my back gas and then close the stage valve (charged, of course).

If I'm just taking the stage in case I need more to finish the dive (e.g. without a surface swim) then I'll dive it valve closed and only deploy it when I need it. If I'm checking my SPG on the back gas the switch should be no surprise.

 

[hroark2112]

I would agree with you except we probably don't dive the same rebreather, which automatically makes you wrong.

Well then....I only have one thing to say.

You're gonna die!!

 

[Peter69_56]

Well I was taught to charge the regulator then keep my sling tanks turned off until the time of use, to prevent a free flow from losing gas, perhaps without my knowledge. This is how I set up my sling tanks/deco/stage etc, with one exception.

As I am travelling, on a regular basis I reach down and charge each sling regulator set. In this way I ensure that each set is charged, and if it has inadvertently lost some gas, hopefully before use its recharged before water enters. You can usually feel a set charge up if gas has been lost during the dive, and in that case I then service the reg set. I do this probably 3-4 times per dive and check the tank SPG as I do.

 

[CuzzA]

With well maintained modern regulators that have dive/pre dive switches and seat adjustment knobs it's nearly impossible for the second stage to free flow, unless the first stage fails and if that's the case the gas is coming out of the tank one way or another. If you rig the second stage in such a way to minimize the chance of physically pressing the purge button I don't see a high risk of diving with the pony tank on and at the ready.

I went through all of this in my mind when I decided to become self reliant and use a pony. Sling it, tank mount it, on or off, inline valve OPRV, etc... At the advice of DD, I tank mount my pony with it turned on and necklace the second stage. I tank mount due to the necessity of having the front of my body clear, but the point here is the second stage is under my chin and I would notice a free flow. While tank mounting may not be the best way compared to slinging, it has its benefits and with all of the great bracket options available today to tank mount it you still have a lot of utility, like handing it off to another diver.

As I and others have mentioned, the pony is a bailout so to speak. It's for emergencies. There's usually nothing calm about emergencies. If I did something so stupid like go OOG or was so unfortunate to have a catastrophic loss of gas, I want to make one action. Grab a second stage, plop it in my mouth and breath.

 

[2airishuman]

Much good advice upthread. Obviously, there's no standard.

I sling a pony and keep the valve off after charging the reg and checking the spg.

Reason being that a slung pony could freeflow in heavy current, and not be noticed. And slung, the valve is right there and only takes a moment to open. I have regs without external adjustments or switches, so I guess there's a somewhat greater chance of freeflow, though I wouldn't depend on a predive/dive switch alone to avoid loss of gas.

 

[KevinNM]

Look at the tech diving, the Deco bottles remain close during all the dive until it is time to use it.

Deco bottles are not your emergency breathing supply during the dive, switching to them is very deliberate because breathing from a deco bottle at the wrong depth will kill you.

Hopefully your pony bottle is breathable at all depths that your main tank is.

 

[shoredivr]

With well maintained modern regulators that have dive/pre dive switches and seat adjustment knobs it's nearly impossible for the second stage to free flow

This isn't true in two cases: diving in current/with a scooter, or in cold water, like we have here in the Great Lakes.

If for some reason a diver is stationary in a current (hanging onto a mooring line, or jamming an anchoring screwdriver into a clay/sand river bottom like in the St Clair River where there is a strong current, while digging out an antique bottle, for example) a free flow can happen. Scootering can cause a free flow too.

But the biggie here is the cold. The water today was 41F. And over the next four or five months it will be even colder. Free flows happen often enough in these conditions, hence I dive with redundancy (sidemount, backmount doubles or single tank backmount with slung tank charged and off).

In water just above freezing, or worse, if the air itself is below freezing, sometimes even breathing through the reg on the surface, without having the reg in the water, will suffice to have a crystal or two of ice form in the second stage. Then pow! Free flow. The cure is switching to the other regulator and turning off the offending tank valve. Sometimes waiting a few minutes will let the water melt the ice, and you can try turning the tank valve on again and things are fine. But often for single tank divers the dive is over, the reg is a ball of ice. That's when slung tanks are vital IMO.

Even hitting the inflator mechanism can cause a free flow if there are water droplets inside it in winter diving.

Just expanding people's horizons. Not all diving is warm water ;-)

 

[Remy B.]

Deco bottles are not your emergency breathing supply during the dive, switching to them is very deliberate because breathing from a deco bottle at the wrong depth will kill you.

Hopefully your pony bottle is breathable at all depths that your main tank is.

I was answering the OP concern of the 1st stage getting water in if not under pressure.

 

[DevonDiver]

If it's a pony, then it's purpose is as an emergency breathing source. Time is critical in emergencies, and you can assume significant diver stress. So my perspective is that it should be stowed open and immediately ready to deliver gas. It should also have a gas source that's breathable at any predicted depth of the dive.

Putting richer nitrox into a pony is really about having an 'ascent bottle', a resource that can help promote more efficient off-gassing in the final phase of the dive. Kind of recreational diver's version of a deco bottle, for added conservatism, but without the hassle of being >40% O2.

Deco bottles are pressurised and shut off during phases of the dive before they're used. I often hear it's to prevent gas loss, but that's not particularly applicable unless you're staging (leaving) the cylinders unattended for a portion of the dive. What tech diver couldn't diagnose and shutdown a free flowing cylinder? And why wouldn't they want the earliest advanced warning of a deco regulator issue? Shutting down deco regulators is, IMHO, a further valuable precaution against accidentally breathing from the bottle below it's gas MOD.

Recently I had a Tec instructor recommend adding one of those inline shutoff valves some times called a free flow valve. I have been considering his advice.

Serves absolutely no beneficial purpose and adds FAILURE and stress potential IMHO. I've never seen a good argument for these in diving of any level....nor heard of any credible tech instructor recommending them. What valve can't you simply shutdown in tech diving??

 

[CuzzA]

This isn't true in two cases: diving in current/with a scooter, or in cold water, like we have here in the Great Lakes.

If for some reason a diver is stationary in a current (hanging onto a mooring line, or jamming an anchoring screwdriver into a clay/sand river bottom like in the St Clair River where there is a strong current, while digging out an antique bottle, for example) a free flow can happen. Scootering can cause a free flow too.

But the biggie here is the cold. The water today was 41F. And over the next four or five months it will be even colder. Free flows happen often enough in these conditions, hence I dive with redundancy (sidemount, backmount doubles or single tank backmount with slung tank charged and off).

In water just above freezing, or worse, if the air itself is below freezing, sometimes even breathing through the reg on the surface, without having the reg in the water, will suffice to have a crystal or two of ice form in the second stage. Then pow! Free flow. The cure is switching to the other regulator and turning off the offending tank valve. Sometimes waiting a few minutes will let the water melt the ice, and you can try turning the tank valve on again and things are fine. But often for single tank divers the dive is over, the reg is a ball of ice. That's when slung tanks are vital IMO.

Even hitting the inflator mechanism can cause a free flow if there are water droplets inside it in winter diving.

Just expanding people's horizons. Not all diving is warm water ;-)

Yes, I'm aware of those other concerns. Current pushing on the purge button can be avoided simply by how you rig up the pony. Cold water diving.... Who dives in 41 degree water? Y'all are crazy.