Pony Bottle, On or Off

[jaycanwk]

Here's a dumb question to the people that sling it, presurize it then turn it OFF,

Why?

I sling mine and leave it on and I can easily see if it leaks or free flows (which it never has) and it is on and ready if I need it so why would I turn it off?

 

[gcbryan]

Here's a dumb question to the people that sling it, presurize it then turn it OFF,

Why?

I sling mine and leave it on and I can easily see if it leaks or free flows (which it never has) and it is on and ready if I need it so why would I turn it off?

I do as you do...however the answer to your question is that those who do it that way do it for their deco gas. They know they must have it as opposed to just needing it in an emergency and having it possibly leak is not acceptable.

To me it taking a good practice for deco diving and misapplying it to the bailout bottle concept to turn it off...but that's the answer.

 

[Doc Intrepid]

Here's a dumb question to the people that sling it, presurize it then turn it OFF,

Why?

I sling mine and leave it on and I can easily see if it leaks or free flows (which it never has) and it is on and ready if I need it so why would I turn it off?

It isn't a dumb question at all.

Just realize that many questions (and answers) are impacted by the diver's environment - for example, you may dive where gill nets are in use. If you don't, then you really aren't familiar with the dangers that that particular hazard poses to recreational divers. So...questions and answers can be environmentally dependent.

Most divers who use pony bottles plan to use them based on some personal scenario. They base what they buy/carry on some pre-identified potential need.

Say for example, a guy who thinks "I spend a lot of time between 90 and 110 fsw, and thats a long way down. If something happens that knocks my dive plan all to hell, say I get entangled in a net or something and use more of my backgas than I planned, I want a completely redundant air source that will get me to the surface regardless".

So the guy takes his respiratory minute volume, and he calculates that in an emergency he may burn gas at a rate of approximately 1.3 cubic feet a minute, which at 100'+ or so for an average diver in trouble may not be far off the mark.

Then he figures he'd need 2-3 minutes at ~100 fsw to unscrew whatever issues he (or someone else) is having; 3 minutes to ascend from 110'-100' to 10' at a rate of 30 fpm (because he pushed his bottom time); 3 minutes safety stop at 10'; and 1 min to ascend slowly from 10' to the surface. So he plans to be on the pony or bail-out bottle for a total of 10 minutes or so. Given the potential for things to get strenuous at depth, he's calculating a straight consumption of around 13 cubic feet minimum. Depending on how deep he goes, and how much task loading actually occurs at depth, gas consumption could be greater than that, but thats why he wants the bail-out bottle in the first place.

The point is that he's planned to have a finite amount of gas on-hand to respond to a worst-case scenario that is pertinent to his specific environment, etc.

When you leave your tank turned on, lots of odd things can occur that will cause you to lose gas. Things get bumped. You assume some odd attitude in the water, and X presses against Y, and you inadvertantly lose gas. Maybe not much - and you're aware of the loss, but its lost gas nevertheless. Maybe - if you happen to be deeper than 100' - you could conceivably lose quite a bit of gas in very little time. And its your bail-out gas...that you've planned on to respond to specific things that may occur in your own specific environment.

The reason guys re-charge their hoses on deep dives is because they lose the internal intermediate pressure between the second stage and the first stage, when the bottle is turned off. Why? Stuff happens. Things get bumped.

You keep bottles turned off because the gas in them has been calculated to meet specified needs. If X happens, you need Y amount of gas, and Y - Z (that bubbled out when your regulator got bumped and began flowing) is not what you had in mind.

Ultimately, if the short amount of time that it takes to turn a valve on to access a bottle is a problem for a diver, that diver is diving close to or beyond their limits. It simply doesn't take that much time to turn on a bottle. Divers who sling tanks ought to be able to remain calm for the matter of seconds it takes to turn on a sling tank and do a gas switch.

When you weigh the possibility of losing gas - possibly a lot of gas depending on how quickly the diver is able to respond (with whatever else is going on) - against the time it takes to turn on a bottle, generally most reasonable guys will conclude that it makes sense to ensure that you have the gas you calculated that you'd need when you need it. Which forms the basis for the argument against leaving your tank on throughout the dive.

Obviously there are other schools of thought on this matter - this is just one guy's answer to your question.

But the next time you put your regulator on your tank, after you charge your hoses, turn your tank off and time how long it takes you to turn it back on.

Don't you think you'd be able to maintain your presence of mind underwater for the matter of seconds it takes you to turn your tank on - if the alternative was possibly losing gas you were counting on?

Just a thought.

Dive safe,

Doc

 

[jaycanwk]

It isn't a dumb question at all.

Just realize that many questions (and answers) are impacted by the diver's environment - for example, you may dive where gill nets are in use. If you don't, then you really aren't familiar with the dangers that that particular hazard poses to recreational divers. So...questions and answers can be environmentally dependent.

Most divers who use pony bottles plan to use them based on some personal scenario. They base what they buy/carry on some pre-identified potential need.

Say for example, a guy who thinks "I spend a lot of time between 90 and 110 fsw, and thats a long way down. If something happens that knocks my dive plan all to hell, say I get entangled in a net or something and use more of my backgas than I planned, I want a completely redundant air source that will get me to the surface regardless".

So the guy takes his respiratory minute volume, and he calculates that in an emergency he may burn gas at a rate of approximately 1.3 cubic feet a minute, which at 100'+ or so for an average diver in trouble may not be far off the mark.

Then he figures he'd need 2-3 minutes at ~100 fsw to unscrew whatever issues he (or someone else) is having; 3 minutes to ascend from 110'-100' to 10' at a rate of 30 fpm (because he pushed his bottom time); 3 minutes safety stop at 10'; and 1 min to ascend slowly from 10' to the surface. So he plans to be on the pony or bail-out bottle for a total of 10 minutes or so. Given the potential for things to get strenuous at depth, he's calculating a straight consumption of around 13 cubic feet minimum. Depending on how deep he goes, and how much task loading actually occurs at depth, gas consumption could be greater than that, but thats why he wants the bail-out bottle in the first place.

The point is that he's planned to have a finite amount of gas on-hand to respond to a worst-case scenario that is pertinent to his specific environment, etc.

When you leave your tank turned on, lots of odd things can occur that will cause you to lose gas. Things get bumped. You assume some odd attitude in the water, and X presses against Y, and you inadvertantly lose gas. Maybe not much - and you're aware of the loss, but its lost gas nevertheless. Maybe - if you happen to be deeper than 100' - you could conceivably lose quite a bit of gas in very little time. And its your bail-out gas...that you've planned on to respond to specific things that may occur in your own specific environment.

The reason guys re-charge their hoses on deep dives is because they lose the internal intermediate pressure between the second stage and the first stage, when the bottle is turned off. Why? Stuff happens. Things get bumped.

You keep bottles turned off because the gas in them has been calculated to meet specified needs. If X happens, you need Y amount of gas, and Y - Z (that bubbled out when your regulator got bumped and began flowing) is not what you had in mind.

Ultimately, if the short amount of time that it takes to turn a valve on to access a bottle is a problem for a diver, that diver is diving close to or beyond their limits. It simply doesn't take that much time to turn on a bottle. Divers who sling tanks ought to be able to remain calm for the matter of seconds it takes to turn on a sling tank and do a gas switch.

When you weigh the possibility of losing gas - possibly a lot of gas depending on how quickly the diver is able to respond (with whatever else is going on) - against the time it takes to turn on a bottle, generally most reasonable guys will conclude that it makes sense to ensure that you have the gas you calculated that you'd need when you need it. Which forms the basis for the argument against leaving your tank on throughout the dive.

Obviously there are other schools of thought on this matter - this is just one guy's answer to your question.

But the next time you put your regulator on your tank, after you charge your hoses, turn your tank off and time how long it takes you to turn it back on.

Don't you think you'd be able to maintain your presence of mind underwater for the matter of seconds it takes you to turn your tank on - if the alternative was possibly losing gas you were counting on?

Just a thought.

Dive safe,

Doc

Thanks Doc, that made alot of sense.


.

 

[dumpsterDiver]

Thanks Doc, that made alot of sense.


.

I agree, plus you only have to have the valve open a turn or so to start breathing from the reg. It should really only take a moment to locate the second stage, stick it in your mouth and BEGIN to open the valve.

 

[Doc Intrepid]

I agree, plus you only have to have the valve open a turn or so to start breathing from the reg. It should really only take a moment to locate the second stage, stick it in your mouth and BEGIN to open the valve.

True - so long as we're talking about bail-out bottles.

(The gas switch procedure for deco bottles is a bit more involved than that, but we're not talking about deco bottles...)

Deployment time for 'opening the valve', though, is the same either way - a matter of seconds. (Different valves require different # of 'revolutions' to fully open. For most divers total # of turns doesn't matter, as dumpsterDiver is correct - the diver can begin breathing off the tank even while continuing to fully open the valve, regardless of whether its an OMS, a Halcyon, or a Thermo valve.)

 

[fdog]

Here's a dumb question to the people that sling it, presurize it then turn it OFF,

Why?

I sling mine and leave it on and I can easily see if it leaks or free flows (which it never has) and it is on and ready if I need it so why would I turn it off?

There's two big reasons - as gcbryan said, for folks that automatically do that, generally it's because their training for handling deco gas / stage bottles / travel gas is that way.

A) Gotta have it; loss of deco gas is a long time at 10'

B) It keeps you from breathing the wrong gas. Put in the wrong reg, and you'll only get a breath or two from a bottle that's always parked "off".


All the best, James

 

[SteveAD]

Another answer to the "why turn it off? " question is in the case of a deco bottle as opposed to a pony bottle. If the diver should inadvertently switch to an O2 rich deco mix at depth (of course there should be procedures in place to prevent this, but one second stage might get confused for another) the limited amount of gas in the hose should not be enough to cause an ox tox hit, and by the time the diver gets to the valve to turn it on he should realize that it is indeed deco gas and switch to the right one.

 

[Dsix36]

solo or buddy diver

sling 1 or 2 tanks, sometimes more

bailout for a rebreather

bottom mix - valve on with reg on necklace under my chin, I will know of a freeflow or slow trickle immediately

other tanks - hoses pressurized and valves off, regs stowed. I might not notice a leak or freeflow as readily

all hoses repressurized regularly during the dive and location of all regs verified by feel. This is for peace of mind in the event of an actual need for bailout.

 

[Dry_Diver]

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

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?

When diving solo I will crack the pony bottle to allow everything to come up to pressure then turn it back off. That will give me two maybe three breaths to turn it back on under water in the case of an emergency. And if it does free flow, you only emptied the hose not the whole bottle. I mounted the bottle in a way that I can easily reach the valve, so turning it on under water was no big deal.

Hope that helps