For those who use a pony bottle to fill your drysuit during a dive?

[Cave Diver]

Scubaroo once bubbled...
but I had a look at my SACs before and after getting my drysuit (I only have 22 drysuit dives), and my average cold water SAC in a wetsuit was around 0.55, and when I started the drysuit, it rocketed to 0.80

<whew!> And I thought it was just me...

 

[Braunbehrens]

Cave Diver once bubbled...


<whew!> And I thought it was just me...

If you find that your SAC is higher with a drysuit that with a wetsuit it may be due to the mammalian diving reflex. Try taking your mask off before you dive, on the surface and putting your face in the water and relaxing.

Of course it could simply be that you have new gear and it creates more stress which raises air consumption.

 

[perpet1]

I used to do a lot of deep diving as well as a lot of group DM work and the ONLY time I used a pony it was clipped to my BC as described above. This was not for any other reason other then to give somone else an independant air source in the event of an emergency. Most underwater accidents occur when somone is stressed (like in an out of air emergency) and the last thing I want to do is have to be in contact with a person in that situation. If the need arises I simply give them air from the pony then clip the pony to them. I them stay close but at a safe distance while we surface. I have had to do this once and I was very happy I had the bottle. If you attach the pony to your drysuit you cancel the biggest safety benefit of the pony all together in that you will havve to maintain contact with a stressed individual if they have an emergency.

I can see a mixed gas situation where you would want to use a pony for your dry suit but this is beyond the scope of 99.9% of the diving world.

For any other reason you are looking at overkill. The air you save from your main tank will probaby be lost to the ineffiency and drag caused by the additional bottle anyway.

 

[DA Aquamaster]

Argon is about the only valid reason to use a pony for drysuit inflation. If you are using tri-mix, you are going deep and A) if you can afford helium you can afford Argon, and B) you would benefit from the added warmth. Using air for dry suit inflation on a tri-mix dive does not make much sense to me.

As indicated above you need an over pressure relief valve as there is no down stream regulator in the sytem and I find that a regulator with an adjustable intermediate pressure is helpful as well.

If you use a pony bottle with Argon you are better off using a low pressure pony (2015 psi). Argon from welding supply companies, like oxygen, is normally not available over 2200 psi and unless you have a wonderfully equipped LDS, you will be doing your own fills via transfill from a larger welding bottle. Your 3000 psi pony won't hold nearly as much as advertised when it has 2000 psi in it at best and ore like 1500 after a couple fills. I use a 14 cu ft low pressure pony and it is more than adequate for a half dozen dive weekend.

You can also run a separate inflator hose from your back gas to use as a backup if you run out of Argon on a dive. I normally attach one along my backplate where it is out of the way but still accessible if I need it.

You will also want to burp your suit, inflate it and burp it again on the first dive, or after removing/redonning your drive suit to remove most of the air and the advantages of Argon on the first dive.

 

[Braunbehrens]

DA Aquamaster once bubbled...
I find that a regulator with an adjustable intermediate pressure is helpful as well.

If you use a pony bottle with Argon you are better off using a low pressure pony (2015 psi).

Do they make regs without an adjustable IP? In any case, a diaphragm first stage is easy to adjust, and you want to keep the IP down around 100.

The nominal pressure of the bottle is irrelevant, what matters is the volume. I use a bottle that holds 6 cuft at 3000 psi, and even at 1500 psi I an execute any dive and probably 2. I find it nicer to have a smaller bottle, and simply buy another one if you need to swap between dives. You wouldn't carry the gas for half a dozen dives on your back, so why do it with an argon bottle. About the only time large argon bottles make sense is if you frequently do dives where you'll need more gas than a smaller bottle can supply.

I am very lucky of course, that my LDS boosts Argon to 3000 psi, but I still have 2 bottles.

 

[DA Aquamaster]

A lot of piston regulators do not have provisions for an externally adjustable intermediate pressure. Many use plastic shims under and/or over the spring (up to four under and one over in the case of most Scubapro piston first stages) that increase pressure by about 5 psi each. Lowering IP below the 120-125 minimum is normally not an option without replacing the spring with something non standard from the hardwear store. Which actually works well for an argon reg that you want to run around 100 psi, but it will make your Scubapro tech scream if he ever sees it.

Many diaphragm first stages can be adjusted externally with a screwdriver to very low pressures if required.

 

[TX65]

I have a Nokia Tek Trilam drysuit with the inflator mounted on the left hip and an integrated bottle pocket.

For most dives, i just use the main gas supply. If the water is really cold, then I use Argon and the mini bottle for the extra insulating properties.