18 Liters Tank

[vixtor]

Hello all,

I have a question for you: until now I always rented tanks, and usually I was finding small sized ones (10-12L). Now, I am thinking about purchasing one, and I am tempted to go as big as possible, to benefit from longer dives. A double is currently too expensive for me, so I am looking at a single tank.

The biggest that I can find is a steel 18 liters, 232 bar tank.

Unfortunately I cannot see the tank (I will order it and it will arrive after some days), so I have some doubts about it. First, I wonder how heavy and negative buoyant it will be, and if I should expect any problems by going that big. From what I have found on the internet, I am expecting it to be about 30kg when full, with a negative buoyancy between -12kg (full) and -8kg empty. As I usually use ~9-11 kg of lead (in a 7mm wet), it seems to me that by using this tank I will need only 2-4 kg of lead, which sounds great. Also, I am asking myself if having such a big weight on my back would not expose me to the risk of rotating face up in the water.

I never had any issues with a 15L tank, and if I remember correctly, once in my youth (about 10 years ago) I have used a double 2x10L tank and it was fine.

May I hope that I will have no problems with the 18L or it would be better to buy a 15L instead?

 

[vixtor]

By the way, please let me know if it would be better to post the units in imperial instead of metric (i can convert them if needed, but my native system is metric)

 

[Tigerman]

There was some discussion about 15l vs 18l in my AOW class as one of the divers was rather big and muscular and used quite a lot of air. The 18l steel tanks supposedly are quite a bit heavier than the 15l ones.

 

[Jimmer]

I could be wrong, but I believe that 18l translates into 108cf low pressure tanks, or 130 cf high pressure tanks here in North America. If that's the case, I can tell you I quite like my Faber lp108's. I dove them briefly as singles, and then doubled them up and haven't looked back. Yes they are heavy (especially as doubles) but if you're physically big and strong enough to handle them, they are very versatile. I doubled mine to get used to them before tech training, but even as singles, there is enough gas in one to be able to make 2 reasonable dives at moderate depths, or do a deeper dive and have a significant amount of reserve gas for an emergency, such as air sharing. The only complaint I have against them is carrying them to and from the boat, so I purchased a folding fridge dolly, that I can use to wheel them back and forth. I only use them for boat dives here in the Great Lakes, as they are a huge pain to try to shore dive with them, at least while doubled up anyway, single they are fine.

P.S. how big are you? These are fairly long tanks as well, and shorter divers don't seem to appreciate them as much as us taller guys.

Jim

 

[vixtor]

What means cf? Is it cubic feet? In this case, a 18L*232bar tank means 4176L, which is about 147 cubic feet.

As for my size, I am 176cm tall (5 feet 9 inches) and 84 kg (185 lbs).

I could be wrong, but I believe that 18l translates into 108cf low pressure tanks, or 130 cf high pressure tanks here in North America. If that's the case, I can tell you I quite like my Faber lp108's. I dove them briefly as singles, and then doubled them up and haven't looked back. Yes they are heavy (especially as doubles) but if you're physically big and strong enough to handle them, they are very versatile. I doubled mine to get used to them before tech training, but even as singles, there is enough gas in one to be able to make 2 reasonable dives at moderate depths, or do a deeper dive and have a significant amount of reserve gas for an emergency, such as air sharing. The only complaint I have against them is carrying them to and from the boat, so I purchased a folding fridge dolly, that I can use to wheel them back and forth. I only use them for boat dives here in the Great Lakes, as they are a huge pain to try to shore dive with them, at least while doubled up anyway, single they are fine.

P.S. how big are you? These are fairly long tanks as well, and shorter divers don't seem to appreciate them as much as us taller guys.

Jim

 

[Jimmer]

What means cf? Is it cubic feet? In this case, a 18L*232bar tank means 4176L, which is about 147 cubic feet.

As for my size, I am 176cm tall (5 feet 9 inches) and 84 kg (185 lbs).

Yes cf means cubic feet, in which case my 108's must be about 17 litre capacity. My advice to you would be to try one sometime and see what you think about it. It is quite tall and quite heavy. For comparison my set doubled up, with the 2 tanks, manifold and bands, weighs about 110 pounds/48kg. I am about 6 feet 2 inches tall, and 230 pounds, so I can manhandle them in and out of the water, but those tanks, even as singles might actually be detrimental to you as far as air consumption. You'll be working quite hard to carry them to and from the water, and you might notice the drag significantly more. If you're interested in more gas capacity have you ever considered smaller double tanks, like 7 litres for example? They would be heavier than one 18 litre I would imagine, but the advantage is doubles tend to be more stable in the water since they don't roll around on your back, and you would have redundancy, whereas with an 18 litre tank, if you have some sort of failure there is no built in redundancy.

 

[pwl]

yikes - that's a *massive* tank, esp at that pressure! what on earth is your consumption rate & how long do you plan to dive at what depth? the weight of the tank itself would be enormous & heavy (about 22kg?)

fwiw faber claim to do a 22L (@232bar) tank : Faber Industrie , but it weighs 25kg!!

in australia tanks with DIN valves can be filled to 300bar - not sure of the EU regulations. maybe using DIN 1st stage would let you get the extra air without the enormous tank?

then again, i guess if you're 150kg and 7' tall it won't matter much either way


... which i see you're not from a post you made while i was typing this.

i'm 173cm and 84kg - my 10.5L tank @ 210 bar gives me about 50min with a bottom of around 15-18m at about 19degrees C. i tend to wear a total of about 18kg including the tank.

lots of variables of course, but i'm wondering if you really need 18L ??

 

[vixtor]

The smallest double available to buy here is a 2x10L@200bar (2x70cf), which looks bigger.

Yes cf means cubic feet, in which case my 108's must be about 17 litre capacity. My advice to you would be to try one sometime and see what you think about it. It is quite tall and quite heavy. For comparison my set doubled up, with the 2 tanks, manifold and bands, weighs about 110 pounds/48kg. I am about 6 feet 2 inches tall, and 230 pounds, so I can manhandle them in and out of the water, but those tanks, even as singles might actually be detrimental to you as far as air consumption. You'll be working quite hard to carry them to and from the water, and you might notice the drag significantly more. If you're interested in more gas capacity have you ever considered smaller double tanks, like 7 litres for example? They would be heavier than one 18 litre I would imagine, but the advantage is doubles tend to be more stable in the water since they don't roll around on your back, and you would have redundancy, whereas with an 18 litre tank, if you have some sort of failure there is no built in redundancy.

 

[pwl]

at the risk of starting a religious war you might want to consider aluminium if you're going to doubles, just since it gets so heavy

 

[Jimmer]

I assume you have access to Faber tanks in Romania. I just looked up the specs for their 9 litre 232bar tank, and by my calculations, a set of doubles with manifold and bands would weigh about 25 or 26kg, compared to 22kg for their single 19 litre 232 bar tank. To put some comparison on that, the 19 litre tank is 75cm long, versus 54cm for the 9 litres. I would expect the double 9 litres would be much more manageable and comfortable for your size than the single 18 or 19 litre.