Buying my first tanks 15l (125) v 12l (100)

Hi I'm looking at buying my first ever tanks and was wondering is the extra gas of the 15L is worth the extra 4 kgs in weight extra. I am looking at Faber steel, there is $50 au difference in price and I will be using them for a mixture of shore and boat dives in Southern Oz all year round. Thanks for the help

Rhino1701:

Hi I'm looking at buying my first ever tanks and was wondering is the extra gas of the 15L is worth the extra 4 kgs in weight extra

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What pressure rating are you talking about? I've got two steel 15L tanks; one 200 bar and one 300 bar. Most of my diving buddies dive steel 10L 300 bar tanks, which basically is the current standard tank for rec diving around here. My 15x200 holds the same amount of gas and isn't noticeably heavier than my buddies' 10x300 tanks, while my 15x300 is a b*tch to handle and lug around. OTOH, with the 15x300 I don't have to worry about running put of gas as long as I dive within the NDL.

Another factor you might consider when choosing tank size is tank length vs your length and the trim of your rig.

The only ones I can seem to find easily are the 232 bar, I asked about the 12L in the 300 bar ( as i have 300 bar din first stage) and the shop said they weigh more than the 15L 232bar so I should just get them. I have a long torso, 190 cm tall 120 kg dry I have the probe hlc bc xl.

I personally opted for a 15L/200bar tank. (i am 180cm tall, normal built) It fits nicely to the dives I am doing and my SAC rate. If doing easy dives, it serves 2 dives. If your LDS fills 232bar tanks well (~270bar warm), then a 12L,232bar is also fine. I find the "normal" 200bar/12L a bit limiting.

Rhino1701:

I have a long torso, 190 cm tall

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In that case, tank length probably won't be much of an issue. If you were short, you'd probably want to stay away from the longest tanks.

You are probably the best person to answer what size tank that would be appropriate for you. What tank size(s) have you been diving with so far? Is the amount of gas in those tanks limiting your bottom time? Are you comfortable with lugging a heavier tank, and is the extra gas worth the work? How much weight are you using?¹ When you think about those questions, you'd probably be a lot closer to answering your original question yourself.

My point here is that there's no one single answer that fits all

Rhino1701:

i have 300 bar din first stage

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That just means that you can use 200bar, 232bar and 300bar tanks as you prefer.



¹ Up here, we dive dry and no matter the weight of the (single) tank, we're never overweighted before we add weight to the belt/pockets. If I were diving wet, I'd risk being overweighted with my 15x300 tank (I use only 3-4 kg with that tank and a dry suit), but if you dive in a thin shorty, a heavy steel tank might make you overweighted even before adding weight.

Can you use the 15L and still have enough weight on your belt/pockets to ditch and be positively bouyant? If so, I'd think the tank is really nice place to carry some of the weight: it gives you gas & extra dive time, and gets some of the weight away from your lower back.

That's the calculation I made when I bought my first tank. Never regretted it & love being able to lend it any time someone could use a little more air (to stay down a little longer with those of us who now dive twins).

If you can get them long 12l are great tanks. the fat short 12l tanks are awful for trim, the 15l move the center of gravity rather far away from the divers back, so my choice would be long 12l, if not available 15l

12L @ 232 is plenty of gas for rec diving. I agree with getting the "longs" if you can find them, they also make good side mount cylinders. I dont agree that the short 12l cylinder trim bad, irrespective of body size or shape.

15l is an overkill. The only upside is that 2 of them make awesome backmount options if you decide to go tech. I use mine for cave and deep dives.

As already put by others:what is your sac rate; were you already short on air (if so with how many liters of air), are you still buyond when dropping your weight, etc.

These are a few questions that you should ask yourself. They might eliminate some configs.


My singles are steel 15l@232bar (3480l / 123cf), but mostly the tankfill is between 190-200bar (cold) (so pay attention when opting for a 200bar bottle, because you might end up with 170bar). For me this is more than enough for a normal dive in local conditions (cold, bad viz, etc).

I have also been diving a colleagues 12l@300bar Carbondive (ok, this adds to the price) and that was a very comfortable config.

Personally I wouldn't go for steel @300bars, as they usually add to much weight.

My advice would be to check for the carbondive bottles @300bar, if the price is not a key criteria.

thanks for the help, i currently have 14 kg (28 lb) of weight with a 12.2 steel and my sac rate on the last dive was around 17. it's slowly improving i think it was around 20 at dive 12 and now i'm up to 18. 64 mins under for about 160 bar max depth was 8 m.