Back mount pony bottle

[Gandalf-the-Diver]

That is a bad idea. Reserve valves have been obsolete for decades. They are mechanically complex and cause more problems than they prevent. Such valves are barely even available anymore and have to be special ordered if you can get them at all.
I don't understand why some divers are trying to over complicate a simple issue. Usually, this stems from being unclear on the basics, and attempting to compensate for doing one thing wrong by doing a bunch of other things wrong as well.
If you need extra gas when real redundancy isn't needed, like for a very long shallow dive, then sling a stage tank filled with bottom mix and use that first before your back tank(s). If you can't monitor your own tank pressure, then you shouldn't be diving at all, and no amount of extra equipment can possibly compensate for being mentally unfit. If you have a mechanical failure, then your buddy has your redundant gas. And if you need a higher level of redundancy than your buddy can provide then buy a real set of doubles with a proper isolation manifold and learn how to manage failures.
But setting up a ridiculous little "pony" tank as a mismatched set of independent doubles is the worst of all possible options. It's like showing up for a race wearing different sized shoes that you scrounged out of a dumpster. Maybe I'm just vain but I wouldn't be caught dead carrying a pony.

The idea, behind that "ridiculous little pony" is for emergencies only; not to extend one's bottom time. The pony should never be included in dive planning. I have been slinging a pony, since my 1st dive as a certified diver. 1st a 13cu tank, then a 30cu tank. One never knows, when real redundancy is needed; breathing off your pony 1st, to extend your dive, is of no help, when all of a sudden, your primary regs have a problem, or a hose blows. In 370 dives, I have used my pony once; and that was around dive 65. I was having issues trying to do my SS in Pea soup visibility, and went OOA. So glad I had my pony. Ones buddy is of no help, when vis sucks, or you are diving solo; I got my SDI Solo cert at dive 170. My local diving, 15'-25' of vis is considered good, and most of my buddies, dive self reliant. One does not need to pack doubles, to have a high level of redundancy. My 30cu pony, will bring me up from 120' and allow me to have a safety stop. I sling my pony, and at 62, have no desire to pack twins.

 

[LI-er]

breathing off your pony 1st, to extend your dive, is of no help, when all of a sudden, your primary regs have a problem, or a hose blows.

If a diver breathes off a pony to extend a dive, relying on the reserve in the main tank to get to the surface and then experiences a primary regulator problem or blown hose, they are in the same exact situation as the typical diver who uses only one tank.

In other words, extending a dive using a pony bottle, while leaving the typical reserve in the main tank does not create any additional risk, while giving the benefit of having redundant air during most of the dive (prior to extending it with the gas in the smaller tank).

 

[Gandalf-the-Diver]

If a diver breathes off a pony to extend a dive, relying on the reserve in the main tank to get to the surface and then experiences a primary regulator problem or blown hose, they are in the same exact situation as the typical diver who uses only one tank.

In other words, extending a dive using a pony bottle, while leaving the typical reserve in the main tank does not create any additional risk, while giving the benefit of having redundant air during most of the dive (prior to extending it with the gas in the smaller tank).

... except, a pony bottle, is NOT for extending a dive. It's sole use, is to be a redundant air source, during an emergency.

 

[grf88]

If a diver breathes off a pony to extend a dive, relying on the reserve in the main tank to get to the surface and then experiences a primary regulator problem or blown hose, they are in the same exact situation as the typical diver who uses only one tank.

In other words, extending a dive using a pony bottle, while leaving the typical reserve in the main tank does not create any additional risk, while giving the benefit of having redundant air during most of the dive (prior to extending it with the gas in the smaller tank).

It is this misuse of a pony bottle that causes it to get a bad rap in some areas. If you want to have extra gas to extend a dive carry a stage or some other form of gas supply. The pony is only for emergencies of which extending you dive is not one.

 

[L13]

Just use tape to label it "Pony" when not using it to extend a dive, "Stage" when using it to extend a dive. Magically, it will now be safe for both uses.

 

[grf88]

Just use tape to label it "Pony" when not using it to extend a dive, "Stage" when using it to extend a dive. Magically, it will now be safe for both uses.

Just not at the same time.

 

[L13]

Just not at the same time.

Correct! you have to change the labels for the magic to work.

 

[grf88]

Correct! you have to change the labels for the magic to work.

Although better defined by their use than a label.

 

[L13]

Although better defined by their use than a label.

Both uses are safe. It is the "Names of Power" that make them unsafe when used with the wrong name. I'm shock by how little knowledge of magic people have around here.

 

[jborg]

So what’s the optimal size for a back
mounted stage used to extend the dive at 100ft? Is a 9cf enough or do I need a 13cf?