Rec Diving a Pony

[Marie13]

This thread has been a great read. My wife and I just picked up 2 AL40 with used apeks dst/at50's after our dive shop suggested it for lake Michigan wreck diving. Until reading this thread, I was under the impression we would just sling the al40 with 2nd stage kept on the bottle with rubber bands in addition to our long hose and necklace.

That’s how I do it and will keep doing it when I dive single tank. I’m not taking my secondary off or anything like that. My configuration will stay the same as when I’m diving my doubles. The only difference will be the number of tanks on my back.

 

[tbone1004]

That’s how I do it and will keep doing it when I dive single tank. I’m not taking my secondary off or anything like that. My configuration will stay the same as when I’m diving my doubles. The only difference will be the number of tanks on my back.

That argument is interesting.
Weirdly, you could actually use your right post from doubles with an added SPG on your single tank if you used the pony as your secondary. If you sidemounted said pony, then it would work even better... You move away from single tank backmount with a pony, to the right side of a set of independent doubles with the left bottle from sidemount.

 

[Marie13]

My single tank set works just fine. I’m not sidemounting anything. Those damned bungees were my nemesis when I did SM and I’m not going back to them.

I’m not a tinkerer. Once something works for me, I generally stay with it, unless it stops working for me.

 

[HKGuns]

Got busy and lost track of this one a bit. Good conversations.

To clarify: For the purpose of this thread I define REC diving as no decompression and Chips are of course POTATO CHIPS! Who calls Merican fries chips?

 

[Kharon]

Blown LP hose or regulator failure are fairly common, ...

Exactly what is your basis for stating this. You got data? Or are you just blowing smoke out your butt and expecting everyone to just accept it. I have never, ever heard of a LP hose blow out and only one reg freeflow. It happened in 42°F water at 106 feet. He was my buddy diving the Radeau (Lake George) and had a pony that he switched to and we did a slow ascent, safety stop with no issues.

None of the club members of 3 clubs (one is NYSDA) has had the problems you say are common. Same with the dive shops in the area and on Bonaire. If you are commonly experiencing those failures you must be awfully negligant re. gear maintenance. So either you're blowing smoke or you don't maintain your equipment. Either way I decline to take advice from such as you. Bye.

 

[wetb4igetinthewater]

Maybe another way to look at it. If you have the pony on a necklace as your second and you use primary donate then your OOG buddy is taking your primary on your main tank and you are breathing your pony. You should not be stressed and consuming significantly more air and the stressed OOG diver has a lot more gas to breath.

"should" is a dangerous word (as is "should not").

Blown LP hose or regulator failure are fairly common, certainly more than manifold failure.

I'm curious as to the source of this claim too. Where can I read the statistics?

 

[doctormike]

I don't have any statistics, and I'm pretty sure that no one does, since there is no system for reporting equipment failures that don't result in fatalities (the vast majority of equipment failures). It was a comment based on me reading this board for many years, hearing people describe accidents, and one unrecoverable free flow of my own that required a post shut down.

In the absence of such a database, it might well be the case that manifold failures are as common as the combined frequency of (1) first stage failures, (2) LP hose failures, (3) unrecoverable free flows and (4) other second stage failures.

In which case, then the advantage of manifolding (access to all of your gas in case of any of those things happens) would be outweighed by the disadvantage of a potential manifold failure. That seems very unlikely to me, but I can't prove it with statistics, so I'll withdraw the suggestion.

 

[johndiver999]

Exactly what is your basis for stating this. You got data? Or are you just blowing smoke out your butt and expecting everyone to just accept it. I have never, ever heard of a LP hose blow out and only one reg freeflow. It happened in 42°F water at 106 feet. He was my buddy diving the Radeau (Lake George) and had a pony that he switched to and we did a slow ascent, safety stop with no issues.

None of the club members of 3 clubs (one is NYSDA) has had the problems you say are common. Same with the dive shops in the area and on Bonaire. If you are commonly experiencing those failures you must be awfully negligant re. gear maintenance. So either you're blowing smoke or you don't maintain your equipment. Either way I decline to take advice from such as you. Bye.

Blown LP hoses IS relatively common on the spectrum of scuba failures. I have seen several instances while being on charter boats over the years which have many customers. In fact I had a hose pop on my friend's regulator just a few weeks ago in the garage. Not surprising really, it was old and tacky and probably should have been replaced just because of the way it looked - but it worked fine with no leaks on a dive a week earlier. I have seen a dramatic one underwater, but generally they blow upon initial pressurization or develop a significant leak - giving warning.

I agree that if the hoses are carefully inspected frequently, the incidence of failure is relatively low, but not avoidable.

Serious catastrophic failures of scuba gear are not that common, but blown hoses are something to consider when talking about potential problems - not doubt in my mind.

 

[Colliam7]

This is a useful discussion for members, because it appears that we may have some very different experiences to contribute.

I have never seen a LP hose catastrophically 'blow' - certainly not saying it cannot, or does not, happen, only that I haven't experienced it, or even seen it, myself. So, I would look at a catastrophic hose failure as a low probability event, based on MY experience.

I have seen multiple cases where a LP, or HP, hose starts to 'bubble' - i.e. somewhere along the hose the inner casing develops a hole and starts venting gas that then very small bubbles seep through the rubber outer casing, usually in several places along the casing, and not necessarily where the actual internal failure resides. I have to periodically replace hoses that do that. I tell students and fellow divers that they cannot expect hoses to last forever, even with 'care'. And, the failures that I have seen, or personally experienced, have usually occurred without any prior visible external sign of a physical defect, i.e. one that some kind of inspection would have 'caught' before the dive. That is also not to say that divers should not regularly inspect their gear, only that even with regular inspection, leaks may develop, at least in MY experience.

It would be interesting to see any actual data, although I doubt that hard data exist. Much of what we 'know' is anecdotal.

 

[halocline]

Really? So, a simultaneous failure with a single and the pony at the same time is more likely than a manifold problem (or any of the failure points that can go wrong in a back doubles system)?!!

I think it is, because the simultaneous failure for single tank and pony could be in two regulators, as opposed to the manifold failure, which is a (sort of) tank valve. Tank valve failures are much less common than regulator failures. So, two of those could certainly be a higher probability than a single valve failure. Most manifolds have 3 consecutive static o-rings guarding the uncontrolled loss of air through the cross bar, (meaning all three would have to fail on a given dive) and a valve seat guarding uncontrolled loss in one of the cylinders in the isolator, and valve stem seals guarding loss in the other cylinder. I'm not sure that there has ever been a confirmed case of isolator failure actually resulting in total gas loss from both cylinders in manifolded doubles.

However, two consecutive regulator failures is also extremely unlikely, unless there were environmental reasons for the failure, like a freeze up. So you're very likely safe with either.