Pony Bottle: Valve On or Off while diving

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VikingDives

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More is always nicer, but a fully redundant (ie essential double tank) is not practical for what I intend...also doesn't answer the original question.

The problem here is that your question is the equivalent of saying, "I'm going to run into traffic blindfolded. Should I wear hearing protection?"

People are telling you not to run into traffic, and maybe if you are going to, you shouldn't do it blindfolded.

Unless you are going to train with it (extensively) and you persist with your present course, I'd recommend you keep it on.
 

Nemrod

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Been musing around the idea of backup/redundant air in the form of a pony bottle for a while now and I've been wondering a few things.

Let's first start with a couple of givens:
  1. 13 ft^3 bottle
  2. Mounted on the main tank or on a Zeagle Zipper attachment on the BC (I have a ranger LTD)
  3. Stage Kit type rigging
    1. SPG
    2. DIN first stage
    3. Second stage with long hose and retainer band

For some reason one potential and routine problem that comes to mind is sudden free flow of the pony second stage, whether at the surface or just because it doesn't like the position, or losing air through an incipient leak through a loose fitting or the like.

My gut says that the pony tank valve should remain closed until needed. Of course this would mean having immediate and ready access to the valve which in turn means the tank should likely be mounted valve down.

Am I barking at the moon or is there some merit to this thought?
I will not get into the size/capacity needed or even the need for a pony bottle, the OP did not ask that. As a solo diver, per SDI, pony bottles are acceptable redundancy for a non-technical solo diver. So then actually on the OPs topic, I turn the valve ON and there are several reasons I do that:

1. Immediacy of need, my need, I am solo and by solo I mean SOLO. Nobody is going to help me but me.
2. Some first stages can lock up if water enters them and while in particular with a DIN valve that might be unlikely it is less likely with the valve on than off.
3. I usually carry a camera, not a small snappie camie, and though it is tethered I want to be able to access my auxiliary air supply and deploy it with one hand quickly and leaving my other hand free for other tasks.
4. I do not want water backing up my regulator from the second stage. Again, a simple downstream reg it should not but purge buttons get jostled and pushed accidentally.
5. I test the aux supply regulator and check the spg before going in. And on the last dive I may switch over for both practice and verification of function just as many divers switch to their secondary for safety stop or do practice drills while on stop.

I usually sling but it would not matter if I was back mounted or slung, the redundant air source should be ready to deploy. My take on it for my purposes.

James
 

NAUI Wowie

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First. Don't use pony bottles, proper planning prevents the need for pony bottles. If proper planning can't prevent the need for a pony bottle then you need a fully redundant setup in the form of doubles or sidemount, both of which take up less space than a pair of tanks and a pony.

If you're going to use a pony bottle, please at least use one that is useful for rock bottom.
For 100ft, that is NO LESS than (4ata*1cfm*3min+2ata*1cfm*3min+1.5ata*1cfm*5min)/.95=26.8cf. That is what it takes to get one diver to the surface in an emergency. First value is conflict resolution, second is ascent, third is safety stop, the /.95 is because only 95% of a tanks pressure is considered usable since you need at least 150psi remaining for the regulator to work. 13cf is nowhere near enough.

Second-if you're going to use one anyway, it should replace one of the second stages on your tank, not be in addition to. I would recommend you replace the second stage around your neck with it and that way if you have a real emergency you pass your primary and switch to the secondary which is then attached to the pony. Leave the bottle on at all times.
I dont know about NOT using ponys. There are circumstances where id say its a good idea like Maria stated on cold water deeper dives when you only have a single tank like a steel 120 or 100. I do that in Monterey and granted its overkill but for me I do like you recomend. I use that as my alternate air so no octo.

But i travel alot so ill be at Coron philippines etc . Doing wreck penetration dives with yes dive leaders but with others that are of unknown skill level. I always request prior to use AL100 tanks on all dives and will only use a dive shop that has them. all other people normally using AL80s. I will fly from USA with my 20ci pony tank and assemble and use that as a backup emergency tank.

For me doing caverns and wrecks in P.I. I think its the smart thing to do.

And as for the on or off discussion, always on. why turn it off? takes a second to have it topped off. if it free flowed oh well at least you know and can fix or refill it when topside. Better to know you have a problem with a pony in advance than to turn it on at 80 ft in a wreck or 100 ft on a reef and have it malfunction when you or someone else is out of air.

I actually did have my pony malfunction and freeflow to empty almost once. After i had the whole top assembly replaced by the dive resort on Cebu in Moalboal for free. I did tip the guy well of course.
 

GJC

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I was taught to turn the valve on pre-dive, test breath the reg, then turn off before entering the water in my SDI Solo class.

I think that while it is possible for water to enter the second stage if the purge gets bumped, the amount would be small and unlikely to get to the first stage and render it inoperable (although servicing it would be a good idea). I think it's far more likely to lose a significant amount of gas if the valve is left on and the second stage purge gets bumped causing a free flow. Therefore, I do what I was taught during my Solo class.

Each diver needs to do their own risk assessment and decide what's going to work best for them.

I would be comfortable carrying a 13 cf pony with a 30 ft depth limit.
 

Moerae

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First, the part relevant to OP:

I vote ON. If your SPG shows a meaningful gas loss at any point, you abort the dive. This isn't a stage, it's your emergency redundancy and you want to avoid any possible panic causing delays deploying it.
Second-if you're going to use one anyway, it should replace one of the second stages on your tank, not be in addition to. I would recommend you replace the second stage around your neck with it and that way if you have a real emergency you pass your primary and switch to the secondary which is then attached to the pony. Leave the bottle on at all times.

Semi relevant to OP:

I think this advice really needs a very important caveat. This should only be done with a pony that has sufficient gas to satisfy Rock Bottom (for yourself). One downside to this arrangement is if your buddy goes OOG and you do not have enough gas in the pony to surface calmly and slowly, you've turned a calm easy gas sharing ascent into a (likely much less practiced) buddy breathing ascent. I know you probably find this obvious but felt it was important to call out given OP's 13cuft. I would not use this arrangement with a 13cuft and with a buddy. OP is solo and 30ft, so might not be totally relevant but felt it was worth pointing out how this impacts gas sharing and planning for gas sharing.

In regards to the other points:
First. Don't use pony bottles, proper planning prevents the need for pony bottles.

Solo aside, I trust my gas planning. Diving to 90ft with a stranger in cold, limited vis, New England water means I have to ask if I trust the stranger's gas planning (and discipline to stick to it) as well. You should see the looks I've gotten when I ask people about rock bottom. And they can agree all day to gas plan the way I suggest but then I have to trust that they stick to it. I don't.

I feel like that's the part a lot of people miss. A pony isn't to make up for bad gas planning, training, or discipline. It's to keep you safe when your equipment fails and you are diving with people you don't know if you can trust. If my buddy goes OOG I don't need to give them the pony or even switch to it myself. I'm following rock bottom. They get my primary I switch to secondary and everything is fine. The pony can be used there for convenience but that's not what it's for.

I agree that other usages (diving too deep on a single tank, factoring it in for your rock bottom, etc) should not be done with a pony. It's not just "extra gas" at that point it's a false sense of security and turns air sharing scenarios into much more dangerous buddy breathing scenarios.
you need a fully redundant setup in the form of doubles or sidemount, both of which take up less space than a pair of tanks and a pony.
I agree and dive doubles on any dive with a stranger in which a CESA would be hairy.

That said I think this misses the fact that 99% of divers do not own and will never own a set of doubles. We should not act like there isn't a reasonable alternative for a fraction of the cost (for the specific use cases of diving with strangers you don't trust or solo diving and needing redundant air).
 

Divin'Papaw

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Another vote for on. Mine is slung as a stage. It’s very apparent if it’s free flowing or leaking. I leave mine on.

Another vote to rethink the 13 cf. I use an AL40 which if more than I need but what I am used to from technical diving and I already own several. For recreational depth an AL30 or possibly AL19 will suffice for most. An AL13 is inadequate unless you have a crazy low SAC or never dive below 60’ or so.
 

GJC

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OP says he is solo doing max depth of 30 ft. A 13 gives him more than 5 min at that depth with SAC of 1 cu ft/min. Need for a safety stop is debatable from that depth. I'd be OK with a 13 in this scenario. If you think you need more, take more.
 

doctormike

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For those pounding the redundancy drum, it’s not uncommon for single tank cold water recreational divers (I’ve seen it quite frequently on the Great Lakes) to carry a pony just in case. I used to do it myself on most dives 60ft and deeper when I dived single tank.

Yup, exactly. There are two reasons why this is a good idea - unrecoverable free flow and a burst LP hose. Both of those can drain a tank in seconds, especially late in the dive when there is less gas.

I don't dive single tank any more, but we have plenty of experienced local divers in this area (NYC) who do, and most of the dive boat captains mandate a redundant gas supply for them. Even leaving aside people who deliberately dive solo, the idea that your buddy will always be there is not something that I would bet my life on.

For those who say that you just need better buddy skills, I say that's a skills solution to a gear problem. :D
 

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