Which tank would you dive first?

[BEM]

Two dives, in fresh water, max depth is 75 feet, 90 min interval. You have a 100 cuft (E7 - steel) and an 80 cuft (aluminum) – both 32% NITROX. My choice is to use the 100, because on the first dive I …

- usually use more air due to being more excited and nervous;
- try to see and do more;
- am able to more easily handle the extra tank weight, than on the second dive;
- usually stay deeper for a longer period.


Makes sense or would you use the 80 then the 100?

 

[lamont]

Makes sense or would you use the 80 then the 100?

ebay. buy 130s.

 

[Mo2vation]

Two dives, in fresh water, max depth is 75 feet, 90 min interval. You have a 100 cuft (E7 - steel) and an 80 cuft (aluminum) – both 32% NITROX. My choice is to use the 100, because on the first dive I …

- usually use more air due to being more excited and nervous;
- try to see and do more;
- am able to more easily handle the extra tank weight, than on the second dive;
- usually stay deeper for a longer period.


Makes sense or would you use the 80 then the 100?

For all the reasons you stated, and if for some reason, the second dive gets scrubbed, you took your best shot first.

I dive a 130. I want max gas.

---
Ken

 

[pants!]

ebay and get matching tanks. Will make your life a lot easier

 

[MXGratefulDiver]

Two dives, in fresh water, max depth is 75 feet, 90 min interval. You have a 100 cuft (E7 - steel) and an 80 cuft (aluminum) – both 32% NITROX. My choice is to use the 100, because on the first dive I …

- usually use more air due to being more excited and nervous;
- try to see and do more;
- am able to more easily handle the extra tank weight, than on the second dive;
- usually stay deeper for a longer period.


Makes sense or would you use the 80 then the 100?

Ordinarily when you're doing multiple dives you'll want to do your most aggressive dive first ... so it makes sense you'll select the cylinder that will provide the most gas for the first dive.

... Bob (Grateful Diver)

 

[LobstaMan]

The 100 first, but for the future, I second the "buy matching cylinders" point of view. That's what I dive...matching PST E7-100s. Cough up the dough and buy another E7 you won't be disappointed!

LobstaMan

 

[RonFrank]

Two dives, in fresh water, max depth is 75 feet, 90 min interval. You have a 100 cuft (E7 - steel) and an 80 cuft (aluminum) – both 32% NITROX. My choice is to use the 100, because on the first dive I …

- usually use more air due to being more excited and nervous;
- try to see and do more;
- am able to more easily handle the extra tank weight, than on the second dive;
- usually stay deeper for a longer period.


Makes sense or would you use the 80 then the 100?

I'd have to look at some dive tables, but you should be able to hit your NDL on the first dive with either tank. I just did a three tank dive on Jupiter using EANX36. I was one bar from Yellow after 45 minutes, and still had over 1000psi of air left, max depther was a bit over 80fsw, but most of the dive was at that depth. I was using E7100's, but found that I could have save the extra rental cost, and just dove with AL80's.

 

[Xanthro]

Related question on this topic, when people are saying you are diving 130s are you passing NDL, or doing more shallow dives?

I'm thinking of getting a couple of 100s, but I reach NDL limits now with an AL80 long before I run out of air, so I'm curios as to the advantages of the super big tanks.

 

[String]

I generally use my biggest tank first as usually thats a deeper and better dive. Second dive tends to be shallower and often less interesting anyway.

15l on dive 1, 12l on dive 2.

Normally 32% in the 15 unless its a specific deep dive and 36% in the 12l

 

[lamont]

Related question on this topic, when people are saying you are diving 130s are you passing NDL, or doing more shallow dives?

I'm thinking of getting a couple of 100s, but I reach NDL limits now with an AL80 long before I run out of air, so I'm curios as to the advantages of the super big tanks.

kind of profile that a 130 would be useful for: EAN32 for 35 mins at average depth of around 90-95 fsw (hitting NDL, maybe a min or two of deco), 10-15 mins at around 40-50 fsw, 15+ mins coming up from 30 fsw. total runtime of 60-80 mins.

also if i try to run the clock out at 60 fsw for 50+ mins on EAN32, i burn around 500 psi/10 mins there so the 130s gas capacity helps.

130s are most useful for multi-level diving, or for that midrange dive between where call the dive due to NDL (deep) and where you call it due to being cold (shallow).