Is there a valid reason for a pony bottle

[leadduck]

That is precisely what a pony does. It allows you to take more gas for a contingency. You can factor such hazards into your plan as a contingency. A contingency for which you would require the gas in your pony. Which is precisely why I carry a pony.

If all you need is more gas for contingency, you might as well take a larger tank and leave the pony at home. The point of the pony is that it is an independent source of gas. When does that make a difference?

For example a cold water backmount diver who isn't able to shut his valves due to a rotator cuff injury. Or maybe he's able to but only slowly in a training situation, and he doesn't feel like he wants to rely on that or his buddy in a real stressful situation. As said above, it's also a personal subjective matter of what kind of redundant gas you feel safe with or not.

Many agencies recommend dual tank valves and two first stages in cold water, although most sport divers are unable to close their own mono tank h-valve without help of their buddy. It's a permanent discussion point in German/Austrian dive forums: why do the clubs recommend h-valve mono tanks while so many members cannot close their own mono tank valves. Should we rather follow BSAC and recommend pony tanks instead of h-valve mono for cold water? Note that all these agencies discourage solo diving. Solo divers usually prefer a truely independent redundant source of gas, and many dive with pony tanks, independent doubles, or sidemount.

 

[flyboy08]

If all you need is more gas for contingency, you might as well take a larger tank and leave the pony at home. The point of the pony is that it is an independent source of gas. When does that make a difference?

For example a cold water backmount diver who isn't able to shut his valves due to a rotator cuff injury. Or maybe he's able to but only slowly in a training situation, and he doesn't feel like he wants to rely on that or his buddy in a real stressful situation. As said above, it's also a personal subjective matter of what kind of redundant gas you feel safe with or not.

Many agencies recommend dual tank valves and two first stages in cold water, although most sport divers are unable to close their own mono tank h-valve without help of their buddy. It's a permanent discussion point in German/Austrian dive forums: why do the clubs recommend h-valve mono tanks while so many members cannot close their own mono tank valves. Should we rather follow BSAC and recommend pony tanks instead of h-valve mono for cold water? Note that all these agencies discourage solo diving. Solo divers usually prefer a truely independent redundant source of gas, and many dive with pony tanks, independent doubles, or sidemount.

At most places, you can’t request larger tanks....period.

 

[CWK]

If all you need is more gas for contingency, you might as well take a larger tank and leave the pony at home. The point of the pony is that it is an independent source of gas. When does that make a difference?

There is a difference between additional gas in a pony and additional gas in a larger tank. I'll try to illustrate the difference in the examples below.

A) Larger tank AL100 or 13 liter.
Start pressure 200 bar. Ascent pressure is 50 bar.
Total gas available at start is 200 bar x 13 liters = 2,600 liters
Total gas available at ascent is 50 bar x 13 liter = 650 liters

B) Standard AL80 (11 liters) plus pony X capacity. Assume that pony is 2 liter so that AL 80's 11 liter plus pony's 2 liter = 13 liter which is the same as the larger AL100.
Start pressure of AL80 is 200 bar. Ascent pressure is 50 bar in the AL80. Pressure in the pony is 200 bar throughout.
Total gas available at start in AL80 is 200 bar x 11 liters = 2,200 liters.
Total gas available at ascent in AL80 is 50 bar x 11 liters = 550 liters.
Total contingency in pony is 200 bar x 2 liters = 400 liters.

The gas in a pony is never taken into account for gas planning for the dive. Ascent pressure is based purely on the gas in the AL80. The pony is purely a contingency.

If you are unclear what difference this makes from the examples above, I suggest that you take the SDI Solo Diving course to learn about gas planning with a pony. I am not an instructor.

 

[doctormike]

If all you need is more gas for contingency, you might as well take a larger tank and leave the pony at home.

As mentioned above, it's usually easier for a traveling single tank diver to rent a pony, or bring one with them, than to get a larger primary cylinder from a dive operator.

The point of the pony is that it is an independent source of gas. When does that make a difference?

For example a cold water backmount diver who isn't able to shut his valves due to a rotator cuff injury. Or maybe he's able to but only slowly in a training situation, and he doesn't feel like he wants to rely on that or his buddy in a real stressful situation.

Not really relevant to this discussion in the basic forum, we are talking about a single tank recreational diver.

Many agencies recommend dual tank valves and two first stages in cold water, although most sport divers are unable to close their own mono tank h-valve without help of their buddy. It's a permanent discussion point in German/Austrian dive forums: why do the clubs recommend h-valve mono tanks while so many members cannot close their own mono tank valves.

A slung pony is so much simpler than an H-valve, and actually offers true redundancy. The valve is right there in front of you. I know that the two training agencies that do solo diving do accept an H-valve, but I have never seen one used. You probably aren't going to be able to rent a tank with an H-valve when traveling, and you need to be able to identify the leaking side and shut it down behind your head pretty quick before your single tank is drained. I don't see the advantage. If you want redundancy AND extra contingency gas, just sling a pony.

 

[CWK]

If all you need is more gas for contingency, you might as well take a larger tank and leave the pony at home. The point of the pony is that it is an independent source of gas. When does that make a difference?

I am in the midst of packing for a red eye flight to Bali tomorrow morning so I am quite distracted.

One easy way to see the difference between the larger AL100 and the smaller AL80 plus pony is to ask yourself how much gas you will have if you have a first stage failure or low pressure hose failure. There will be a big difference.

 

[tursiops]

I know that the two training agencies that do solo diving do accept an H-valve, but I have never seen one used.

Actually, PADI's Self-Reliant says this in its instructor manual for the specialty:
Redundant gas source - pony cylinder, twin cylinders with isolation valve or
sidemount configuration. Redundant gas supply must be configured so that
the diver can access it with one hand.

The H-valve is mentioned in the SDI standards, but so is a SpareAir....so take that for what it's worth.

 

[grf88]

How to rig a pony bottle?

 

[doctormike]

Actually, PADI's Self-Reliant says this in its instructor manual for the specialty:
Redundant gas source - pony cylinder, twin cylinders with isolation valve or
sidemount configuration. Redundant gas supply must be configured so that
the diver can access it with one hand.

The H-valve is mentioned in the SDI standards, but so is a SpareAir....so take that for what it's worth.

OK, that makes sense. I did SDI solo.

 

[saxman242]

Koolaid? Nah, science bruh.

What does science say happens different at 101 feet than at 100 feet and everyone reacts the same to?

 

[Fastmarc]

Actually, PADI's Self-Reliant says this in its instructor manual for the specialty:
Redundant gas source - pony cylinder, twin cylinders with isolation valve or
sidemount configuration. Redundant gas supply must be configured so that
the diver can access it with one hand.

The H-valve is mentioned in the SDI standards, but so is a SpareAir....so take that for what it's worth.

I don't remember seeing these mentioned in SDI Solo book. I remember them basically recommending nothing less than a 25 cf.