Pony tank thoughts/advice?

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@ghost9 yes, I'm certainly aware of the strong opinions on SB, but like always, the info here is super helpful!

It's slightly embarrassing to admit, but this thread pointed out my misconception that a mounted pony's second stage would be tethered to the tank (I hadn't envisioned actually routing the hose to my body like the primaries; I was thinking of it more like a "spare air style" handoff item). With that clarified, the two options certainly make a lot more sense.

Since my typical diving is not the style that would warrant a second bottle, I feel like I've got a lot of freedom to play around with it and find my comfort zone and preferences. I'm actually kind of excited to start experimenting with the pony... I look at any safety redundancy as a plus, and it'll be a useful skillset to have if/when I decide to advance to deeper or more "technical" diving.

I'm glad you're getting good info. There are some people that will tell you there is only one way to do things, and that may be true if you're going to consider yourself a certain type of certified diver. There is nothing wrong with that for them but it may not be for you. The tech world has come up with allot of good ideas that can be translated to recreational diving, others don't do so well. Do you really need an 6 or 8 foot secondary hose for a shallow water dive in Cozumel?

Remember every style you dive has trade offs, all of them. Your diving style might make a large pony bottle both unnecessary and cumbersome ie shallow beach dive and kayak diving. If you dive to depths greater than 80' (for me anyway) you probably need something bigger than a 19cf bottle.

I would suggest that you take your pony to an easy site and breath it down at depth. See how long it lasts. Refill and do an accent using it. Same for a horizontal swim. Get very familiar with the properties of the tank under water and that may help you decide how or even if you want to continue using it.

When you decide how you want to mount or sling the bottle, use it in a controlled environment to get very comfortable with it's limitations. When an emergency happens the stress level goes up and things that aren't second nature can become stressful to the point of failure. I've heard stories of people diving with pony bottles that never even tried to use them when they ran out of air.

Last but most importantly, have fun trying this. Playing with new gear is always fun!

Good diving.
 
I would suggest that you take your pony to an easy site and breath it down at depth. See how long it lasts. Refill and do an accent using it. Same for a horizontal swim. Get very familiar with the properties of the tank under water and that may help you decide how or even if you want to continue using it.

This is great advice, thanks, I'll try that. It's one thing to do this mathwise starting with RMV and multiplying out the depths and times, quite another to simply take a stab at it and see how far the tank goes.

By the way, there is quite a bit of talk about transfill whips in this thread. I dive high pressure steels as my main tanks (3442psi / 230 bar), and my pony is a lower-pressure aluminum (3000 psi / 200 bar). If I'm topping off from a higher-pressure tank to a lower-pressure one, do I run a risk of overfilling it? Or do they have a reg built in?
 
This is great advice, thanks, I'll try that. It's one thing to do this mathwise starting with RMV and multiplying out the depths and times, quite another to simply take a stab at it and see how far the tank goes.

By the way, there is quite a bit of talk about transfill whips in this thread. I dive high pressure steels as my main tanks (3442psi / 230 bar), and my pony is a lower-pressure aluminum (3000 psi / 200 bar). If I'm topping off from a higher-pressure tank to a lower-pressure one, do I run a risk of overfilling it? Or do they have a reg built in?
I don't think you'll have too much of a problem unless your HP has allot of volume, like bigger than a 120. If you're taking 13 cf of air out of an HP100 that tank will drop to 87cf at 3000 psi.

To be honest, I've never had to trans-fill a pony because I'v had a buddy with a compressor. I'm sure someone here can give you the math. I'm just calculating the pressure drop to remove 13cf from the 100HP.
 
This is great advice, thanks, I'll try that. It's one thing to do this mathwise starting with RMV and multiplying out the depths and times, quite another to simply take a stab at it and see how far the tank goes.

By the way, there is quite a bit of talk about transfill whips in this thread. I dive high pressure steels as my main tanks (3442psi / 230 bar), and my pony is a lower-pressure aluminum (3000 psi / 200 bar). If I'm topping off from a higher-pressure tank to a lower-pressure one, do I run a risk of overfilling it? Or do they have a reg built in?


This is why you definitely want to have a pressure gauge on your fill whip - you can figure out what pressure is in each tank by manipulating the tank valves. If you were just topping off a pony and need to add just 400 psi, it would not be hard to over pressurize the pony without a gauge. It is nice to be able to start each dive with the pony full. Having the whip makes that a lot easier.

Perhaps it is not obvious, but you would hook up both tanks to the whip. then turn on the lower pressure tank and you can read the pressure. then you turn off the lower pressure tank and turn on the higher pressure tank. then you get a reading of the high pressure side.

Then you can turn the hp valve off and open the LP tank valve fully. Then.. you sloowly crack open the HP tank and watch the pressure. When it gets up to desired pressure, you shut down the HP valve, then close the LP valve and then purge the whip.
 
To be honest, I've never had to trans-fill a pony because I'v had a buddy with a compressor. I'm sure someone here can give you the math. I'm just calculating the pressure drop to remove 13cf from the 100HP

I had a good rapport with my last dive shop, so they would top off my pony gratis. If I emptied it, I'd pay for a fill. Although I have a whip, being down a couple of cuft on my 19 pony doesn't bother me, with a 13 I might be more picky, depending on the dive.
 
I had a good rapport with my last dive shop, so they would top off my pony gratis. If I emptied it, I'd pay for a fill. Although I have a whip, being down a couple of cuft on my 19 pony doesn't bother me, with a 13 I might be more picky, depending on the dive.

My local quarry will top off or fill a pony for a regular at no cost.
 
Ah, one other question: In the thread linked by Marie13, there are several suggestions for purchasing a "transfill whip". I confess that I'm not familiar with this device, but at a glance, it appears to allow the transfer of air from one cylinder to fill another(?).
An inexpensive, but not very fast option, is @couv 's $2.50 transfill solution; Tank Equalizer for $2.50
I use a slight variation of this, and it is slow.... which isn't a bad thing if yo are topping off from an HP cylinder to an LP or aluminum (easy to check pressure regularly and not over fill).
And for the record, I sling a 19 on the right side (due to muscle memory from other training) when I carry a pony. 28 inch hose, tucked in retainers that are cheap ball bungies from harbor freight (makes it easy to re-stow the hose even with gloves).

Respectfully,

James
 
https://www.shearwater.com/products/swift/

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