Question The Right Dive Tanks: Autonomy vs. Tradition

[Njord fr]

I'm facing a dilemma... Soon to be level 2 (PADI AOW) and moving to level 3 in September (autonomous at 60 meters). I'm also heading towards cave diving, which means gearing up accordingly. I'm having a hard time getting permissions from my club to borrow tanks for diving... even though I have the opportunity to get in the water... very frustrating. I think buying my own tanks would make me more autonomous and thus less frustrated. Fellow divers (all into cave diving) suggest purchasing two tanks, either 7.5 liters, 10 liters, or 12 liters, for reasons including:
- More autonomy (obviously)
- More possibilities for progression (sidemount, double tanks, independent back mount, etc.)
- The ability to consider cave diving with my own equipment soon

They say that with the standard single 15-liter tank, I'll soon be limited... and it's not usable for cave diving.

If I were to listen to myself, and not necessarily considering cave diving (I train a lot in quarries), I'd think two tanks are quite reassuring, regardless of how they're arranged. If a regulator fails and empties one tank, there's always the second... with a single tank, it's more complicated.

In short, I'm a bit lost.

What do you think?

 

[Lorenzoid]

Diving in cold quarries and already looking forward to the possibility of training to see those amazing caves you have in France? Listen to your fellow divers!

 

[grantctobin]

I'm facing a dilemma... Soon to be level 2 (PADI AOW) and moving to level 3 in September (autonomous at 60 meters). I'm also heading towards cave diving, which means gearing up accordingly. I'm having a hard time getting permissions from my club to borrow tanks for diving... even though I have the opportunity to get in the water... very frustrating. I think buying my own tanks would make me more autonomous and thus less frustrated. Fellow divers (all into cave diving) suggest purchasing two tanks, either 7.5 liters, 10 liters, or 12 liters, for reasons including:
- More autonomy (obviously)
- More possibilities for progression (sidemount, double tanks, independent back mount, etc.)
- The ability to consider cave diving with my own equipment soon

They say that with the standard single 15-liter tank, I'll soon be limited... and it's not usable for cave diving.

If I were to listen to myself, and not necessarily considering cave diving (I train a lot in quarries), I'd think two tanks are quite reassuring, regardless of how they're arranged. If a regulator fails and empties one tank, there's always the second... with a single tank, it's more complicated.

In short, I'm a bit lost.

What do you think?

What is rationale for you not getting permissions?

D12s.

 

[Imla]

D12s

D7s are too small for tech/cave and D10s are horrible to trim out.

 

[lowwall]

So the issue is you need access to a 15L tank now, but expect to be using different tanks in the future?

You need to tell us something about what the options are there. Can you rent tanks as needed for the short term for a reasonable price? Is there a used market for 15L tanks (so you can more or less break even by purchasing a used tank now and reselling it later)?

Finally, how certain are you that you won't be diving single tank again locally once you move to doubles? Many divers end up with dedicated single and double tank rigs.

 

[rjack321]

1x D12 is fine for most single tank diving - which is generally shallow-ish, nobody is doing 35m+ in single around here. When sidemounted 2x D12 is realistic and ideal for colder water cave diving.

 

[Njord fr]

What is rationale for you not getting permissions?

D12s.

it's about the people involved. The sea divers don't want to dive in the cold quarry, and the only person willing to supervise me is not favored by the club's president, leading to difficulties in obtaining permission.

 

[rick00001967]

fwiw.....if you are thinking of getting into cave diving then your goal should def be to eventually start diving double sidemount.

the choice of which tanks to use is greatly influenced by the type of sm rig you will be diving, is it fresh or salt water, and the water temps you will be in.

some sm rigs are better suited for heavy steel tanks, while others may be best using allum.

many divers that dive cold water prefer the heavier steel tanks so they do not need as much added lead. some sm rigs are not really designed very well to hold a lot of added lead.

while some will still choose to use allum in cold water because they prefer how those tanks behave in the water compared to steel. they can handle them easier. they may also have a rig that can properly hold any extra lead needed.

in either case, you can certainly dive smaller tanks in double sidemount if you choose to. but obviously your gas is limited when compared to larger tanks. this would be a big draw back in a cave.

as i think someone mentioned, you may also want to choose tanks that could also be used if/when you decide to do a dive in single backmount. versatility is always nice to have.

i personally started sm using heavy steel 77 cu ft tanks. i didnt like them. i ended up with a pair of steel 72 cu ft tanks made in the 1960's and really liked them once i found a pair that behaved equally in the water (i was shocked how different each tank behaved in the water). they behave similar to allum 80's.

in mexico for example the allum 80's are very common to use in cave diving. i believe that is the same as your 12 litres? the water there is fresh (salty in some parts) and not as warm as the ocean, but is only about 70F or so.

 

[grantmac]

2xD12s for colder water sidemount.

 

[lowwall]

Can someone who speaks European and American tell us if the D12 is the same or nearly the same as an HP100? Is it filled to 232 bar?

If so, that would make the 15L basically the HP120. Is that really a standard for single tank in France? The standard here would be the HP100 or Aluminum 80 (11L at 207 bar), with the HP120 not uncommon, but regarded as kind of a specialty tank for air hogs.