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

[LI-er]

This is incorrect.

If you have two gas sources then you have redundancy. Having a cylinder partially drained doesn't somhow eliminate the usefullness of the remaining gas.

I said almost the same thing but you said it better with less words.

 

[lexvil]

Having not wanted to delve to deep into the redundancy of this topic yet still having my 2 cents…

Pick one extending bottom time or safety based redundancy. If the former use it first if the latter just end your dive when you hit your personal reserve.

 

[Tom_Ivan]

I said almost the same thing but you said it better with less words.

You set me up. I hit it home. Don't worry I'll give you the credit

Pick one extending bottom time or safety based redundancy.....

No. Pick both.
The op will drain one cylinder down leaving enough gas to reach the surface.
He will then drain the other cylinder down leaving enough gas to reach the surface.
He will then proceed to the surface with 2* the minimum gas required to reach the surface.

Thus he has selected to increase bottom time and ALSO increase his redundancy.

 

[SouthernSharktoothDiver]

@Tom_Ivan @LI-er Thank y’all very much! Like, I hate to be disagreeing with so many comments, but a lot of people are just like, “you should just use a bigger tank” with little explanation as to why, and some of them are leveling criticisms based on assumptions that directly contradict my stated gas plan, so I appreciate y’all sticking up for me.

 

[NW Dive Dawg]

@Tom_Ivan @LI-er Thank y’all very much! Like, I hate to be disagreeing with so many comments, but a lot of people are just like, “you should just use a bigger tank” with little explanation as to why, and some of them are leveling criticisms based on assumptions that directly contradict my stated gas plan, so I appreciate y’all sticking up for me.

I'm in the "you should just use a bigger tank" camp if your goal is to simply get another 10-15 minutes of bottom time. The explanation as to why...... is that this will allow your redundant 19cf to be truly and fully redundant throughout the entire dive.... and other than the occasional top-off with a transfill whip, no need for vis inspections or cost to keep the 19 full and good to go.

 

[MaxBottomtime]

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.

 

[Wibble]

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?

 

[MaxBottomtime]

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.

 

[happy-diver]

a good exercise would be, to get on your little tank before you hit reserve on your big
tank and when you hit reserve on your little tank, get back on your big tank then complete your dive

Thank y’all very much!

 

[SouthernSharktoothDiver]

@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.