Gotta love that Pony

[Crush]

There is no trying to troubleshoot and then reach up, back, and over to locate and then to shutoff exactly the correct valve(s) while you could be slightly narc'd, and for sure slightly panicked.

You are a brave, brave man...

FWIW, you can isolate either tank and breath off whatever regulator is hooked up to the non-damaged side of the manifold. But I think that you will soon receive the same information from others, only in greater detail...

 

[TSandM]

You are correct -- a pony bottle is more like independent doubles; the two parts of the gas supply are completely separate from one another. But, of course, that means that, if you have a problem with one half, you lose all access to that part of your gas. With manifolded doubles, you can shut down the offending post, and retain access to all of your gas, except in the very unlikely event of an actual manifold problem. You trade the possibility of that for the much higher likelihood that you will be able to shut down a freeflow or leaking regulator and not lose half of your breathing supply.

 

[AfterDark]

I like independent doubles, two single tanks each with a regulator,SPG,and octopus carried like connected doubles. They are simple and redundant. If your so inclined you can add a pony bottle, size of your choice to add to the redundancy. The BC can be connected to the tank you intend to use second with a backup LP hose on the pony. The 1st tank can be breathed down to 300 psi. or leave enough for a slow ascent and SS or use one octopus and leave enough for your buddy to ascend and do a SS. Start with all valves on and ready to use. All three of my second stages have different features I can feel to tell them apart without looking. Monitoring the SPG's will show a serious leak and give time to switch over to another reg. IDs IMO give the diver a lot of options without a lot of task loading, ie turning valves on and off ID'ing bottles etc...

 

[Doc Harry]

I like independent doubles, two single tanks each with a regulator,SPG,and octopus carried like connected doubles...

It seems to me that if you carry independent doubles on your back instead sidemount, don't you lose some of the advantages of having independent doubles?

 

[halocline]

But, doesn't a Pony bottle offer a higher degree of redundancy than doubles???
With doubles isn't the manifold Isolation Valve a "single point" failure mode?

The isolation manifold would need to fail in multiple spots for gas to be lost uncontrollably through it. This is virtually impossible, despite the fantasy-land scenarios occasionally cooked up about the manifold hitting an overhead and breaking apart. On my manifold there are 3 consecutive o-rings on each side, which means for all the gas to be lost either all 6 o-rings would have to fail or all 3 on one side plus a failure of the iso valve.

What the isolation manifold gives you in return for this extremely remote chance of failure is access to the gas in both cylinders in the event of a regulator freeflow on either post. Regulator freeflows are at least 1000 times more likely than a catastrophic manifold failure, (that's a guess in case anyone wants statistics) so IMO it's a pretty good trade off.

IOW, it's many times more likely to have regulator free flows on all your tanks on the same dive than it is to have an iso manifold failure.

There is the added diver responsibility of shutting the isolation valve down, but that's what training and practice are for.

 

[AfterDark]

It seems to me that if you carry independent doubles on your back instead sidemount, don't you lose some of the advantages of having independent doubles?

Such as? I've never carried a tank anywhere but on my back. I don't see the advantages of side mounting and it certainly looks uncomfortable and like it would be in the way. To each their own.

 

[garethscottnet]

Because a CEPD (Controlled Emergency Plummeting Descent) is not an option, nor is turning to your buddy and giving him the "out of parachute, share parachute" sign.



For some ridiculous reason people seem to think that skydiving is a good analogy to use to make comparison to scuba diving.

Other than the word "dive" the two have pretty much NOTHING in common.

Driving sounds like Diving so how about comparing a pony with a seatbelt then?

I hope you put it on I also hope never need it.

 

[Dr Wu]

Not all of us...

:cool2:

That has to be an old photo. There is no way those people lived long with those tank boots.

 

[jaycanwk]

Wow. Alot of people are feeding the Troll.

He is going to get quite fat.

 

[TechBlue]

That has to be an old photo. There is no way those people lived long with those tank boots.

NE divers, not cave.