How to figure out the best tank to buy?

[BigTuna]

How should I go about figuring out the best tank for me? A requirement is not to be (much) heavier than an Al80. A loose requirement is somewhat more air than an Al80. I'd use DIN fittings, and I'd dive singles only. I'd be diving on wrecks, mostly, off the New Jersey coast, and I'd leave the tanks home for resort diving (naturally).

How would I pick between these two steel tanks, for example:
- Worthington LP85 (2400 psi +10%), weight 34, buoyancy full/empty -1/-6
- OMS C100 (3400 psi), weight 33, buoyancy full/empty -1/-8.
Would the high pressure OMS tank be the better choice, since it has more air and basically the same numbers as the Worthington? If it is, why would anybody ever buy the Worthington?

Does the LP85 have 85 cuft at 2400 psi, or is it 85 cuft at +10% (2640 psi)?

I've read that cave divers would select low pressure tanks, while wreck divers would select high pressure tanks. Why is that?

I'm assuming I want steel, so I can get more air for the same weight--is that the way to go?

 

[TechBlack]

I would suggest the hp 100. It's a nice compact size, at 3442, you'll get 100cuft, and still get 80cuft at 2640, at 3000 it'll give you 91 cuft. Do you'll get a good deal more gas than an al80, at a similar weight, with a more compact size. They trim pretty nicely, and you'll love the buoyancy of them.... Very nice in a drysuit. The finish of the oms is much more durable than the paint of the worthington, that'll help in the long run.

the 85 is 85 at 2640, they are 77 cu at 2400, the same as an al80.

High pressure is preffered for the reasons above, they give you more gas at a higher pressure, but still give reasonable volume at lower pressures.

Good luck with it....

 

[BigTuna]

I would suggest the hp 100. It's a nice compact size, at 3442, you'll get 100cuft, and still get 80cuft at 2640, at 3000 it'll give you 91 cuft. Do you'll get a good deal more gas than an al80, at a similar weight, with a more compact size. They trim pretty nicely, and you'll love the buoyancy of them.... Very nice in a drysuit. The finish of the oms is much more durable than the paint of the worthington, that'll help in the long run.

the 85 is 85 at 2640, they are 77 cu at 2400, the same as an al80.

High pressure is preffered for the reasons above, they give you more gas at a higher pressure, but still give reasonable volume at lower pressures.

Good luck with it....

Thanks. Can I move my regulator DIN fittings from LP to HP if I change my mind?

 

[TechBlack]

Actually the nice thing about the pst (oms) tanks are that they are still considered intermediate pressure tanks. Federal regs technically only require din fittings on pressures higher than 3500 psi. But check your reg to make sure that the yoke is rated to the correct pressure. You don't want to put a 3000 psi max yoke on a 3400 psi tank for obvious reasons. If you want to go din, by all means go for it, just make sure that all your regs are compatible with all your tanks, you don't want half your tanks din and half yoke. If you can get away with it, keep the yoke and save yourself some cash!

 

[francousteau]

the 85 is 85 at 2640, they are 77 cu at 2400, the same as an al80.
Good luck with it....

By my understanding, your quote is not correct. A LP 85 gives you 85cf of gas @ 2400psi. The 10% is an overfill and therefore would give you the equivalent of 119cf of gas at 2640psi. This is the nice thing about low pressure tanks. I run with Faber LP108's and get them overfilled to a minimum of 3000psi, which gives me the equivalent of 135cf of gas. With high pressure tanks, there is no overfill rating (but people overfill those to some degree anyway ).

 

[TechBlack]

By my understanding, your quote is not correct. A LP 85 gives you 85cf of gas @ 2400psi.

Actually I used to think this too, but when having the tanks hydroed, some shops were not getting the "+" renewed and this was causing under fill problems with the lp tanks. The advertised volume is at the give pressure of 2400+ which is 2640. My double 104's yeild close to 240 cu at 3000, my double lp80's give me 182 cu at 3000, not that I recommend that sort of thing!!!

 

[docmartin]

some answers in loose order:
You can use DIN regs on LP and HP tanks. this is merely a matter of the tank valve you are using.
LP tanks tend to be less expensive.
Cave divers like LP because they overfill them and get huge amounts of gas.
+ rated tanks like an LP85 reach their stated capacity i.e. 85cf at the +rated pressure i.e. at 2640psi.

 

[francousteau]

+ rated tanks like an LP85 reach their stated capacity i.e. 85cf at the +rated pressure i.e. at 2640psi.

Really, you take 10% off the cubic footage of the tank at the 2400psi rating? This pretty much sucks then and I'm left wondering why not just rate the tanks at 2640psi if they're going to call the tank a 85cf'r? After all, if the tank doesn't come back from hydro with the + rating, you're left with something other than the 85cf tank that you thought you were buying.

 

[TechBlack]

Really, you take 10% off the cubic footage of the tank at the 2400psi rating? This pretty much sucks then and I'm left wondering why not just rate the tanks at 2640psi if they're going to call the tank a 85cf'r? After all, if the tank doesn't come back from hydro with the + rating, you're left with something other than the 85cf tank that you thought you were buying.

that's the beauty of it!!! problem is most shops never check for the plus, and you end up getting overfilled anyways.... you have to watch out sometimes with lp's. I've had shops assume mine were hp, just because they were galvanized, and luckily enough saw the error before they were filled to high

 

[docmartin]

that's the beauty of it!!! problem is most shops never check for the plus, and you end up getting overfilled anyways.... you have to watch out sometimes with lp's. I've had shops assume mine were hp, just because they were galvanized, and luckily enough saw the error before they were filled to high

i hear the boys and girls in cave country have them pumped up to 4000psi. riding the rocket...