Info Are Pony Bottles Dangerous?

[SlugLife]

A pony tank becomes dangerous if it causes the diver to move his secondary reg from the main tank to the pony bottle, leaving the main tank with just one reg.
Doing so can result in the incapability of employing a large amount of gas stored in the main tank if the primary reg fails.
Using a pony tank should always be simply "incremental" to the standard setup, not a trade-off between the main tank and the auxiliary one.

If the pony-bottle does not have sufficient air to safely surface, the diver isn't using a pony-bottle correctly.

Personally, I do remove the octo and don't consider it even slightly dangerous, given I always have enough air to surface in both tanks, and in the event of a failure, will surface. If the chances of a failure in a 2 minute window are 1/1000 (which would be really high), the chances both fail at the same time would be 1/1000000.

I am curious though, how often are 2nd stage failures, where they fail to deliver air? It's not something I've heard about happening. (To be clear, I'm not suggesting it doesn't happen, just that I don't hear about it.)

edit: This is a good example of the snake-eyes analogy in my previous post. There may be a slight increase in risk to yourself removing the octo, but the addition of a (properly used) pony bottle can more than compensate for that risk. It's a similar concept to how many solo divers use pony-bottles, while buddy-divers use their buddy for redundancy.

 

[Wibble]

Redundancy. Simply calculate the amount of gas you need to get yourself to safety from the WORST point in your dive. Then bring that gas.

Show your workings that include:

• SAC/RMV at an elevated breathing rate, maybe a CO2 hit
• Allowing time to get your act together at the worst possible time
• Including all safety and decompression stops
• Including any gas changes

For a recreational dive, this is simple arithmetic.

For a technical or rebreather dive, it is standard operating procedure.

 

[Still Kicking]

I also know precisely what you're doing, and you do too, setting an unrealistically high bar.

.i am genuinely curious about how often they are needed. Thanks for referencing your incident - glad it wasn't deeper and more catastrophic.

In ~ 3000+ dives, I can only think of one incident where i would have switched to a bailout: deep night dive, grabbed a tank that hadn't been filled, rushing and didn't check pressure. Basic stupidity! Fortunately my buddy was there so it worked out. It was not the kind of dive I would do solo.

I get your point though - you can't post about the dive you don't survive .....

 

[Angelo Farina]

If the pony-bottle does not have sufficient air to safely surface, the diver isn't using a pony-bottle correctly.

Personally, I do remove the octo and don't consider it even slightly dangerous, given I always have enough air to surface in both tanks, and in the event of a failure, will surface. If the chances of a failure in a 2 minute window are 1/1000 (which would be really high), the chances both fail at the same time would be 1/1000000.

I am curious though, how often are 2nd stage failures, where they fail to deliver air? It's not something I've heard about happening. (To be clear, I'm not suggesting it doesn't happen, just that I don't hear about it.)

edit: This is a good example of the snake-eyes analogy in my previous post. There may be a slight increase in risk to yourself removing the octo, but the addition of a (properly used) pony bottle can more than compensate for that risk. It's a similar concept to how many solo divers use pony-bottles, while buddy-divers use their buddy for redundancy.

I have never seen a 2nd stage failure. Instead I witnessed dozens of 1st stage failures, and had a couple of occurrences my self.
Most frequent is O-ring extrusion, but also filter clogged and valve closed due to hitting rocks.
That's the reason for which I use only tanks with two valves and two fully independent regs. An octopus with a single first stage is not safe enough for me...

 

[Wibble]

I have never seen a 2nd stage failure. Instead I witnessed dozens of 1st stage failures, and had a couple of occurrences my self.
Most frequent is O-ring extrusion, but also filter clogged and valve closed due to hitting rocks.
That's the reason for which I use only tanks with two valves and two fully independent regs. An octopus with a single first stage is not safe enough for me...

Freeflows are very common

 

[SlugLife]

2nd stage failures, where they fail to deliver air?

I have never seen a 2nd stage failure

Freeflows are very common

I think angelo was mostly referring to unable to deliver air. I'm familiar with freeflow, that's ultra common. Basic free-flow, which can be stopped, has happened to me plenty of times. I've never experienced a "catastrophic" free-flow, but certainly heard of them.

Given this topic has been nagging at me for some time (before this thread), I decided to create another thread on the "2nd stage fails to deliver air" topic:

Redundant Octos & 2nd Stages Unable to Deliver Air?

Disclaimer: This is an advanced thread, I do not advocate beginner-to-intermediate divers ditching their octo. In a thread about pony-bottles, the topic of whether or not to ditch your octo came up. Specifically, someone mentioned being unable to access your larger air supply, if you use a...

scubaboard.com

 

[Wibble]

Feathering a valve to breathe from a freeflowing second stage. Will call that a win for sidemount but with the caveat that it is a very unlikely use case for manifolded doubles — can shutdown the freeflowing side and breathe from the working one.

 

[Waterwulf]

Something has been bothering me in this thread and I just can't keep it in anymore. All this discussion of pony bottles, double tanks with separate valves and first stage systems, triple second stages, minimum gas this and that, quadruple redundant dinkle whoppers, minimum pressures, etc. etc. etc. All in the name of making a dive as safe as possible while still being exciting.

Ok, so what happened to the built in reserve, the "J valve"? That was a built in reserve that was factory set at 500 PSI and could be adjusted up to 750 PSI. I still remember my training on it the early 70's. It was intense. The whole class walked around for six months waving our left hands behind our backs looking for the handle like we were waving away stinkers. lol.

 

[NW Dive Dawg]

Something has been bothering me in this thread and I just can't keep it in anymore. All this discussion of pony bottles, double tanks with separate valves and first stage systems, triple second stages, minimum gas this and that, quadruple redundant dinkle whoppers, minimum pressures, etc. etc. etc. All in the name of making a dive as safe as possible while still being exciting.

Ok, so what happened to the built in reserve, the "J valve"? That was a built in reserve that was factory set at 500 PSI and could be adjusted up to 750 PSI. I still remember my training on it the early 70's. It was intense. The whole class walked around for six months waving our left hands behind our backs looking for the handle like we were waving away stinkers. lol.

J Valves were originally a result of no SPG's. You still have that exact same reserve amount in your main tank at all times..... Just need to pay attention as to when you get that reserve point. If you have an AI computer, just set an alarm for 750 or 500 and you'll have the same benefit of the J valve without the need to find and pull the rod extension.

What a J valve cannot do is provide redundancy to mitigate a catastrophic failure of your primary system.

The J Valve also has the problem of a potential for the "lever" to be inadvertently or accidentally actuated.

 

[Wibble]

Something has been bothering me in this thread and I just can't keep it in anymore. All this discussion of pony bottles, double tanks with separate valves and first stage systems, triple second stages, minimum gas this and that, quadruple redundant dinkle whoppers, minimum pressures, etc. etc. etc. All in the name of making a dive as safe as possible while still being exciting.

Ok, so what happened to the built in reserve, the "J valve"? That was a built in reserve that was factory set at 500 PSI and could be adjusted up to 750 PSI. I still remember my training on it the early 70's. It was intense. The whole class walked around for six months waving our left hands behind our backs looking for the handle like we were waving away stinkers. lol.

What was your typical dive profile back in the day?

Does that differ from the typical dive profile nowadays?

Consider gasses, tank volumes, depth, bottom time, decompression profile, etc. What about bend statistics and numbers of dives? Impact of technology now and then.