Back mount pony bottle

[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?

 

[Angelo Farina]

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).

The additional risk arises if the primary tank has only one main reg and no secondary reg. Most people using a pony install only a single reg on the main tank. I instead always use two (complete, two first stages, two second stages, on two independent valves - and my main 15-liters steel tank has also the reserve).
So, when using a pony (not always, in my case, but only for "heavy tasks"), I end up with THREE complete and fully independent regs, each with its own valve.
At that point, however you use your pony, it does never diminish safety compared to not having it.
But if the pony means moving the secondary reg from the main tank to the small bottle, then you could have a problem: if the primary reg fails, you have no backup on the main tank...

 

[Angelo Farina]

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?

I do not really understand what those "cf" mean. I use a 3 liters pony at 200 bar (600 liters total).
Typically I attach it in the middle of my twin tanks (2x 9 liters at 200 bar), or beside my single tank (15 liters at 232 bars). In both cases the main tank has two independent valves, two fully independent regs and reserve.
This is a good redundancy, in my opinion, for demanding dives (when crossing the border to tech, which in reality I did in the past only a very small number of times and I am not doing anymore in the last 25 years).
But here we are in "basic scuba" forum, so I understand that my pony setup is "overkilling" here...

 

[34109411]

I do not really understand what those "cf" mean. I use a 3 liters pony at 200 bar (600 liters total).
Typically I attach it in the middle of my twin tanks (2x 9 liters at 200 bar), or beside my single tank (15 liters at 232 bars). In both cases the main tank has two independent valves, two fully independent regs and reserve.
This is a good redundancy, in my opinion, for demanding dives (when crossing the border to tech, which in reality I did in the past only a very small number of times and I am not doing anymore in the last 25 years).
But here we are in "basic scuba" forum, so I understand that my pony setup is "overkilling" here...

Cf : cubic feet