Go to a larger tank or not

[StrangeDoc]

I already have a 100cuft steel HP tank. I want to get a second tank (I should have gotten it when I got the one). The shop that I normally would buy a tank from is out of the 100cuft tanks right now and won't have any for a couple of weeks at which point they likely will be on sale for a short period of time. Another shop has one that I could get at a similar price that I paid for the original. Now I was also considering a 117cuft tank as well and kind of going back and forth on getting a 117cuft or just picking up another 100. Just wanted to see what thoughts others have on going with the little bit bigger tank? Right now the 100cuft is lasting me about 45 minutes from about 3500 PSI.

 

[tbone1004]

the issue with the 117 is it is a larger OD so you have to adjust the cam bands every time you switch. only you can determine if you are willing to deal with that.

 

[scubadada]

I already have a 100cuft steel HP tank. I want to get a second tank (I should have gotten it when I got the one). The shop that I normally would buy a tank from is out of the 100cuft tanks right now and won't have any for a couple of weeks at which point they likely will be on sale for a short period of time. Another shop has one that I could get at a similar price that I paid for the original. Now I was also considering a 117cuft tank as well and kind of going back and forth on getting a 117cuft or just picking up another 100. Just wanted to see what thoughts others have on going with the little bit bigger tank? Right now the 100cuft is lasting me about 45 minutes from about 3500 PSI.

Hard to tell what your gas consumption is as you don't give a depth. Forty five minutes is not long on 100 cf at moderate depths. Do you know your RMV? Are your dives gas or NDL limited? Do your dives last as long as your usual buddies? The answers to these questions may help you choose another tank. If you are taller, you could opt for a 120 cf steel tank, same diameter as your 100.

 

[StrangeDoc]

sorry depth was around 50ft or so... and usually everyone else is outlasting me at the moment, I am still fairly new so my consumption is a bit high

 

[Akimbo]

You also want to consider how close you will get to your no-decompression limits. No point dragging a bigger tank around if you can only burn up a single 80 on your reped. Another consideration is you might want to accumulate an identical cylinder if you ever want to make them into a doubles set.

 

[shurite7]

Putting aside the NDL, tbone has a good point. Having to change your BCD strap between dives can be a pain. If your air consumption is higher than the others a ST120 will work for depth, then use the ST100 for the shallower dive. A Worthing ST120 is a little taller than an AL80, where as a Fabre ST120 is a couple inches taller than an AL80.

 

[StrangeDoc]

It would probably be better to get another tank of the same size thinking about it. The idea of readjusting several things between dives even right now I don't think would have been that bad until my straps develop more of a memory but the idea of in the future being able to go doubles which I am likely to do at some point in time would be nice.

 

[scubadada]

sorry depth was around 50ft or so... and usually everyone else is outlasting me at the moment, I am still fairly new so my consumption is a bit high

So, if you are diving your cylinders down to about 500 psi, at an avg depth of 50 ft, your RMV is about 0.75 cf/min, a bit on the high side. Somewhere around 0.5 cf/min is about average. You can easily calculate your own RMV DiveNerd - SAC Rate / RMV Calculator, Imperial Units. You will likely improve markedly with more experience, improved buoyancy and trim, and relaxation.

These are the RMVs from 271 divers replying to surveys on SB in 2009 and 2016:

 

[boulderjohn]

I think tbone1004's point is a key issue, and if i were you, I would probably get another HP 100. For single tank divers, that is a really nice tank.

 

[RyanT]

+1 for another HP 100. Just keep diving and work on your buoyancy and kicking skills. The less work that you do by fiddling, inflating, kicking, etc., the better your gas consumption becomes. An HP 100 is really all the tank that most recreational divers ever need.