Open or closed valve on pony bottle?

[The Chairman]

I have no tech training, but that sounds like a really bad idea

The joys of ignorance.

Rebreather divers often use this so they can reduce the amount of tanks they carry. The same tank can be used as bailout or as off board dil. If you're using it as offboard dil, you want to be able to isolate that second stage in case there is a free flow. There are various ways to approach this scenario with either side condemning the other. To keep things consistent with my OC tech diving, I charge the cylinder, breathe the bottle and then turn off the cylinder. If I utilize it, the first thing I do is verify the contents while I'm turning it on. Then I either start to breathe on it (bail out) or I plug it in to my block (off board Dil), and adjust my PDC either way.

 

[dumpsterDiver]

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.



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??

On a boat i used to dive from, we had an oxygen tank on board and a 20 ft hose to the second stage. The shut off valve at the second stage was very helpful in avoiding wasting of a limited supply of oxygen due to free flows when throwing the second stage in or, the not so frequent error of forgetting the hose is hanging and driving away for a while. It seemed to work well, and the consequences of confusing on and off were minimal.

 

[lerpy]

@dumpsterDiver I use the inline valves on my stages, and the point you make has validity, however the key to a lot of things in diving is doing it the same way always so you have the memory. If using a reg with an inline valve, I always open the tank valve and leave open. As you say in this case and OPG is important to avoid hose burst.

As for the original question, if I am carrying a pony, ie meant as a redundant source in event of emergency, then I leave the valve open. The bottle is with me at all times so I can monitor the pressure to ensure I still have a full tank.

If I have a stage, then I charge the line and shut the valve off before I drop it. You do not want to leave a tank valve on when dropping a stage as current, or a bump, or a leak of some description could result in returning to a bottle that you need that is no longer full.

 

[dumpsterDiver]

@dumpsterDiver I use the inline valves on my stages, and the point you make has validity, however the key to a lot of things in diving is doing it the same way always so you have the memory. If using a reg with an inline valve, I always open the tank valve and leave open. As you say in this case and OPG is important to avoid hose burst.

As for the original question, if I am carrying a pony, ie meant as a redundant source in event of emergency, then I leave the valve open. The bottle is with me at all times so I can monitor the pressure to ensure I still have a full tank.

If I have a stage, then I charge the line and shut the valve off before I drop it. You do not want to leave a tank valve on when dropping a stage as current, or a bump, or a leak of some description could result in returning to a bottle that you need that is no longer full.

I agree that finding a system and following a certain protocol will simplify things and reduce errors. A reasonable guideline and goal. However another important principal pertains to simplicity.

Adding the OP relief valve and in-line valve to a pony bottle to be used in a recreational setting is adding complexity where it is unneeded.

What would you do if you saw that the OPV was starting to burp some air? I bet you would shut down the tank valve, huh? Now you would be outside of your usual routine and in a real emergency you might mess up with the in line valve due to the stress.

I am not as diligent in simplifying my diving rig as I should, for example, I carry two inflator hoses on my reg, one for an Air 2 and the other for a standard inflator - in the rare case that I use a different BC with a standard inflator on it.

Everyone just needs to carefully consider what benefit they get from adding "stuff".

 

[CuzzA]

Everyone just needs to carefully consider what benefit they get from adding "stuff".

Funny you mention that.

When going to an Air2 I realized after the fact my DiveAlert would make the system too bulky and cumbersome to comfortably breath from. After a shark encounter and unable to get the boat's attention I decided the DiveAlert was going to be part of my rig. So I added another inflator hose that is banded to my SPG hose and dedicated for the DiveAlert and it also serves as an excellent inflator for DSMB deployment (plus don't tell anyone, but you can breath off those things ). I never considered I could use that inflator hose to dive a different rig without an Air2.

I weighed my options and chose the probability (benefit) of a quick exit from the water before I get eaten because of the DA over the added failure point of another hose. I also considered if I were diving dry (which I don't) then I'd still have the same amount of failure points as anyone else who uses a drysuit and uses their back gas for inflation.

 

[dumpsterDiver]

yeah the air two and the Dive alert is a cluster. I have a few some for air 2 and some regular but i think they are all broken. They are nice but due to the fact that they are high frequency, they are really loud next to your ear, but 750 ft upwind, there is so much attenuation, nobody can hear them..

I am using a woven hose for the air 2 supply. It is reasonably comfortable to use, plus if I every really have to use it, comfort will probably not be an issue.

Reminds me of another screw up I had, this one is with inflators...an example of added complexity bites me in the azzzzzzz.

 

[CuzzA]

Indeed, the boat being significantly up wind leaves you with just visual signaling. Though the last few times I've been out I've told the fellas I want to continue to test it out if I surface any decent distance away. So far they've alway heard it, but I don't recall which direction the wind was blowing in those tests.

A tip I learned, tested and have shared in the case of a free flow of gas from a reg, inflator, cut or blown hose is to simply bend the hose like you would to shut off a garden hose.

In that situation perhaps throwing a Dive Alert on the spare inflator would be a good idea. You can use it to inflate a bag and if it did free flow, just disconnect it. Plus it would avoid confusion.

 

[dumpsterDiver]

yeah I've never had to fold a hose over yet. Wonder if I would have thought of that eventually.. Probably just loosen my waist strap, raise the tank a little, reach back and shut off the tank and come up on the pony..

 

[Bigbella]

Pressurized with valve off, if it is handy; on, if mounted out of sight . . .

 

[TMHeimer]

Pressurized with valve off, if it is handy; on, if mounted out of sight . . .

That sounds right. Mine's a 13cf mounted on tank.