Info Are Pony Bottles Dangerous?

[Angelo Farina]

The only real difference is twice the weight and gas. If your dive plan uses a lot of gas, there's little reason one cannot use doubles.

???
My single tank is a 15 liters Faber at 232 bars
My twin tanks are Technisub Aralu, 9+9 liters at 200 bars. Both tanks contain the same amount of gas (roughly 3600 liters) and weight almost the same.
The twin tank is more stable on your back and the trim is easier.
Twin tanks do not need to be very large, they are often small and compact..Here in Europe for rec diving currently the preferred size is 7+7 liters...
Only problem is that they are more expensive.
When I needed more air, I also used a pony: it is perfectly compatible with twin tanks, you attach it easily in the center of them.

 

[billgraham]

If you're looking to save money, this is the wrong sport, check out bird watching!

 

[jborg]

When I needed more air, I also used a pony: it is perfectly compatible with twin tanks, you attach it easily in the center of them.

I was 100% with you up until this point, given that I’m usually a double-7 diver. However, when you’re already diving doubles and find that you need more gas, that’s the point where a bigger double set is appropriate. The D12 being the standard for anything slightly deeper or more complicated than the usual rec dive.

(More gas than that and a stage, I guess it’s rebreather territory.)

 

[SlugLife]

My twin tanks are Technisub Aralu, 9+9 liters at 200 bars. Both tanks contain the same amount of gas (roughly 3600 liters) and weight almost the same.

I was thinking about double-full-sized tanks when I wrote that. You're correct. Twin 40cu is about the same weight as a single 80cu. (etc)

If you're looking to save money, this is the wrong sport, check out bird watching!

I'm not sure if that's a response to me or another post. There's a difference between spending $1500, $15000, and $150000.

There are ways to be frugal, smart, and prioritize how you allocate your money. If I intended to drop about $15k, I'd probably start looking at rebreathers, scooters, or compressors. Though I could definitely see some people allocating that towards a dozen small scuba-tanks to run sidemount or double-BM, especially if you have back or knee problems.

While perhaps not "ideal" it doesn't bother me to run sidemount 80cu + 19cu pony, which is what I usually run on dives less than 60ft.

 

[billgraham]

I was thinking about double-full-sized tanks when I wrote that. You're correct. Twin 40cu is about the same weight as a single 80cu. (etc)


I'm not sure if that's a response to me or another post. There's a difference between spending $1500, $15000, and $150000.

There are ways to be frugal, smart, and prioritize how you allocate your money. If I intended to drop about $15k, I'd probably start looking at rebreathers, scooters, or compressors. Though I could definitely see some people allocating that towards a dozen small scuba-tanks to run sidemount or double-BM, especially if you have back or knee problems.

While perhaps not "ideal" it doesn't bother me to run sidemount 80cu + 19cu pony, which is what I usually run on dives less than 60ft.

My point is more that when you go to buy something, whether it's a reg or a valve or a computer, buy the best you can get your hands on and it always makes sense to buy gear that you can use down the road, when your capabilities increase.

 

[Angelo Farina]

I was 100% with you up until this point, given that I’m usually a double-7 diver. However, when you’re already diving doubles and find that you need more gas, that’s the point where a bigger double set is appropriate. The D12 being the standard for anything slightly deeper or more complicated than the usual rec dive.

(More gas than that and a stage, I guess it’s rebreather territory.)

Point is that another set of doubles is truly expensive. As said, I used a pony perhaps 10 times. I have 1200 dives...
Buying a 12+12 for using it so rarely?
Nonsense..
And already owning the pony for other useful purposes, in those rare cases I needed more air, I attached it to my Aralu.
Actually Technisub was selling it as a kit, very nice and streamlined, as you can see:

 

[34109411]

Another good one that I did, also deco gas but relevant: I had a single tank with an H-valve and a slung 30 with O-2. I got to my 20 foot stop and grabbed the O-2 reg with my free hand, pulled it out and the first stage (yoke) was just hanging there. Doh! Depressurized and fell off so I got rid of that the same week in favor of a din reg and

Point is that another set of doubles is truly expensive. As said, I used a pony perhaps 10 times. I have 1200 dives...
Buying a 12+12 for using it so rarely?
Nonsense..
And already owning the pony for other useful purposes, in those rare cases I needed more air, I attached it to my Aralu.
Actually Technisub was selling it as a kit, very nice and streamlined, as you can see:

nice

 

[happy-diver]

What gets expensive with manifolded 7 litre tanks, is the second set required for the second dive

 

[Tanks A Lot]

....
My single tank is a 15 liters Faber at 232 bars
My twin tanks are Technisub Aralu, 9+9 liters at 200 bars. Both tanks contain the same amount of gas (roughly 3600 liters) and weight almost the same.

I know you know the exact math behind this, but I just want to throw it out there, as it always amazes me by how much the benefit of increased pressures diminishes rapidly.

While the naive calculations of 15 x 232 = 3480 | 18 x 200 = 3600 give a difference of 120L, the real calculations look different.

At 20°C the 15L cylinder at 232bar will hold 3271L.
At 20°C the 9L+9L at 200bar will hold 3421L.

The real difference here is 150L, not 120L. If you think of it, it's 30L wasted for the increase in pressure.

If one goes to really high pressures of 300bar or TRIMIX with high He mixtures, those differences can become staggering really fast and go into the 3 digit range - Not insignificant for exact dive plans.

A small set of doubles charged to a lower pressure is objectively better in most regards, besides price, than a single cylinder charged to a high pressure.