Why extra air when solo?

[2airishuman]

I'll give you a good reason. I've dived solo most of my 57 years on SCUBA. One day I decided not to attach my pony to my main tank as I planned to go to just 40 fsw. However, a large bat ray caused me to descend to nearly 80 fsw as I filmed it. Then, suddenly, no air was flowing thru my reg. I made an emergency ascent from that depth. At first I thought the fill station had failed to fill my tank, but then remembered I had checked my air pressure as I walked to the sea. Turns out that a tiny piece of debris had fallen into my valve's dip or debris tube and clogged it. Only had that happen once in all my years, but it happened. The unexpected. If I had put my pony on before descending it would have been no problem.

Thank you for that. That is the second firsthand report I've read describing that failure case.

 

[MaxBottomtime]

I'll give you a good reason. I've dived solo most of my 57 years on SCUBA. One day I decided not to attach my pony to my main tank as I planned to go to just 40 fsw. However, a large bat ray caused me to descend to nearly 80 fsw as I filmed it. Then, suddenly, no air was flowing thru my reg. I made an emergency ascent from that depth. At first I thought the fill station had failed to fill my tank, but then remembered I had checked my air pressure as I walked to the sea. Turns out that a tiny piece of debris had fallen into my valve's dip or debris tube and clogged it. Only had that happen once in all my years, but it happened. The unexpected. If I had put my pony on before descending it would have been no problem.

Didn't you originally post that the dip tube had come loose and was clanging around inside your tank?

 

[2airishuman]

Seven

A better answer is that it depends on your gear configuration and exactly what it is you're removing when you remove an octo from you kit.

I dive primary donate. If I'm buddy diving then my gear configuration is:
40" primary hose
Necklaced secondary

If I'm diving with a pony, the pony bottle is slung on my left side with its own 40" hose and reg bungeed to the bottle.

Now, in that configuration, removing my necklaced secondary isn't going to achieve much streamlining, because it's out of the way and has a short hose. It would also get me out of the habit of putting on my neck bungee on every dive, which is problematic because it's dangerous to forget. I suppose I could remove my 40" primary hose and swap the primary and secondary regulators (they're tuned differently) and have the bungeed primary, only, which would accomplish some streamlining. But if I had to share air, I would no longer be able to use primary donate, because the hose is too short. I would have to donate the pony reg.

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Another common configuration among divers who use pony cylinders is to dive an Air2 (or similar competing product), again using a 40" hose on their primary. For a back-mounted pony, the reg can go on a necklace, or with a slung pony it stays on the bottle.

There's nothing to remove here, unless you swap out the Air2 for a standard power inflator, which doesn't streamline anything. Maybe it removes a failure point but I think you'd be hard pressed to find an example of the 2nd stage in an Air2 failing in such a way as to contribute to an emergency.

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Now if you're still diving using the "octo donate" configuration, well, I suppose you could just take the octo off and put in a port plug, and maybe you should, especially if you're using a back-mounted pony. (Maybe you should think about switching to primary donate, too, but that's another topic.) Because reg mixups while diving ponies are a thing, and there have been at least two fatalities as a result.

 

[chillyinCanada]

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[Zef]

There have been fatalities where someone has their air off and mixes up their pony and backgas regs, which is IMO the biggest risk of diving with a pony.

Can you cite any examples of this actually happening or is this one of those REO Speedwagon cases..."Heard it from a friend who heard it from a friend who heard it from another..."?

-Z

 

[MaxBottomtime]

Accident on Southern Cal Oil Rigs Dive
"Although he had a steel 100 (29.7% Nitrox) on his back, Hank ran out of air at the nine minute mark because, at the beginning of his dive, he mistakenly put the regulator from his bailout 19 cu ft cylinder into his mouth instead of the reg attached to his primary 100 tank. He unknowingly breathed the entire dive off his much smaller bailout bottle. Upon postmortem analysis, his main 100 tank was virtually full. (Just a tiny amount gone that would’ve been necessary for him to add air to his drysuit on the way to depth.)"

 

[Bob DBF]

A better answer is that it depends on your gear configuration and exactly what it is you're removing when you remove an octo from you kit.

I dive primary donate. If I'm buddy diving then my gear configuration is:
40" primary hose
Necklaced secondary

I dive the same configuration, and when adding the pony I choose not to change that configuration for the same reason. Also I dive solo in some locations and off dive op boats where sometimes i am in proximity to other divers. Since my pony is sized for my needs, i would rather share my back gas, and me switch to the pony if necessary, rather than constrain a rescue to my solo timetable.

My pony always has air, regardless of back gas, due to safety concerns and cost.



Bob

 

[2airishuman]

Can you cite any examples of this actually happening or is the one those REO Speedwagon cases..."Heard it from a friend who heard it from a friend who heard it from another..."?

-Z

I'm aware of two. One's in A&I, the other was related to me by a diver friend of the decedent who was expressing genuine concern that I was going to kill myself with my pony bottle.

 

[pauldw]

I'm aware of two. One's in A&I, the other was related to me by a diver friend of the decedent who was expressing genuine concern that I was going to kill myself with my pony bottle.

OK, so clearly the thing to do is to wash out my BC with vodka before diving so there are no microbes in there, and then if there's trouble while diving, breath in and out of the BC if there's nothing coming out of the regs. Which ought to work for a few breaths, and the vodka fumes may improve the experience. Seeing as an alternate air source could kill me, and all.

(For members for whom English is not their first language, this is a stab at humor.)

 

[2airishuman]

OK, so clearly the thing to do is to wash out my BC with vodka before diving so there are no microbes in there, and then if there's trouble while diving, breath in and out of the BC if there's nothing coming out of the regs. Which ought to work for a few breaths, and the vodka fumes may improve the experience. Seeing as an alternate air source could kill me, and all.

You dive the way you want. If you want to sell out a good thread for a bad joke, well, that's your choice too.

The point is that some configurations pose risks. There are ways to mitigate the risks and there are configurations that are safer. I think back-mounted pony cylinders are inherently more risky than slung (or twinsets or sidemount or independent doubles). If you're going to back-mount a pony then you have to figure out how to mitigate the risk of a mixup. There are various strategies, some of which are mentioned upthread. It also doesn't hurt anything to watch your SPG; if it doesn't go down 10 minutes into the dive that could be an indication that you're not on back gas. One of the mitigations is to be sure you can reach your valves and operate them, because dives that start with the valve on the back gas off are often part of the accident chain.