On using a small tank to increase bottom time and provide redundancy

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I had a buddy who would suck his 130 cu ft tank down, then switch to his pony for the ascent. He would suck it down, then switch to whatever amount he had left in his 130 to surface. He ran out of air multiple times and said he came up on fumes a few more times. He is no longer allowed to dive with us.
Out of curiosity, was there any obvious reason for his lousy gas consumption?
 
Out of curiosity, was there any obvious reason for his lousy gas consumption?
He had great air consumption. At around 5'5" and maybe 150 pounds, he would be down longer than I would. We usually let him drop 10-15 minutes before us and we would still be back at the surface before him on most dives. Twice he had to come up to us underwater to share air. The liability became too much for us. After that, we instituted a no-pony bottle rule on our boat. I know it isn't fair, but there is too much room for abuse like our buddy did and it's our boat, so our rules.
 
@MaxBottomtime not trying to like, cause an argument or whatever, but I don't really get how the pony bottle was the issue for this guy. He didn't leave enough gas to turn around. That's bad diving, and I fully agree that you have a right to kick him off your boat for that, but what's the pony got to do with it? If he doesn't know to leave a reserve, it wouldn't matter if he had one tank or 40.
 
@NW Dive Dawg I'm not actually that familiar with transfill whips. Is it safe to use one without getting the occasional hydro test? I would assume it carries a similar risk of pressure failure as a compressor, but as I said, I know very little about them.
 
@MaxBottomtime not trying to like, cause an argument or whatever, but I don't really get how the pony bottle was the issue for this guy. He didn't leave enough gas to turn around. That's bad diving, and I fully agree that you have a right to kick him off your boat for that, but what's the pony got to do with it? If he doesn't know to leave a reserve, it wouldn't matter if he had one tank or 40.
Like the OP, he wasn't using the pony as an emergency reserve, but to extend his dives. Twice, he even had inches of water in his pony from purging it while it was empty. I told him if he doesn't have a pony with him, he can't abuse it. We later decided it was better just to keep him off our boat.
 
I wonder if that type of behaviour naturally follows those with ideas of blundering around in high current
low vis, hunting shark teeth, with no buddy, unsure of CESA, so incorporating in their plan a pony instead
 
@NW Dive Dawg I'm not actually that familiar with transfill whips. Is it safe to use one without getting the occasional hydro test? I would assume it carries a similar risk of pressure failure as a compressor, but as I said, I know very little about them.

Here's a snip of my transfill whip. Its a means of either equalizing two tank pressures.......or utilizing a higher tank pressure to "fill" a smaller cylinder. My whip is DIN on both ends with pressure relief valves on both ends and a gauge to monitor and confirm the transfer. If transfilling from a DIN tank to a Yolk tank then I use adaptors.

For example, my 19cf pony is AL with a max rated pressure of 3000psi. My steel 100's and 120's are HP rated to 3500psi. So if I deplete my pony at all for any reason then I can transfill it back up to max working pressure.

Since I am transfilling myself and the risk is all on me, then I am fine forgoing the annual VIS inspections...... but I still make sure to keep all of my tanks in current Hydro.

Hope that makes sense.....

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@happy-diver if you’re going to criticize my plan, would you please explain why what I’m doing is a bad idea? Cause the whole point of this thread was get an actual, fact based reason what I have in mind is a bad idea. “I think you’re too dumb to watch an spg” is not a valid reason, since even if that were true, it’d be equally true no matter what gear I carried.

If you have an actual, substantive reason why what I’m doing is a bad idea, I’d love to hear it. If not, I’m really not sure what you think you’re accomplishing being snarky on the internet, but I hope it works out for you
 
@NW Dive Dawg this makes sense to me. I don’t have my setup ready to go yet anyway, so I may as well look into using a transfill in the mean time, cause the $10-20 per year viz fee always did kinda rub me wrong. Thanks for the advice!
 

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