hp vs lp tanks

[jiveturkey]

Thinking of finally buying my own set of tanks. I see there are high pressure and low pressure tanks but I'm not sure why I'd choose either. I usually dive aluminum 80s but have recently bought a drysuit and I think i'd like to get steel tanks. I'll be more comfortable with some of that extra weight on my back instead of my hips.

So what's the difference between hp and lp? Is it just that hp is shorter? Any preference? why?

 

[lamont]

So what's the difference between hp and lp? Is it just that hp is shorter? Any preference? why?

get the hp tanks. for the same water volume tank (same effect on the overall weight you carry) you will get more gas. for the same volume of gas you will have a smaller tank. even if you only get 3000-3200 psi fills, its still better than the 2640 psi LP tanks (unless you consistantly get 3000-3200 psi overfills on the LP tanks).

there are people who like the LP tanks better because of the buoyancy characteristics (where the balance of the tank is and how it shifts when it drains, which is a function of the distribution of steel in the tank), but people get the HP tanks to trim out fine, and if you have no preexisting preference, going for the LP tanks doesn't seem worth the hassle.

of course you may be able to pick up some LP104s from someone who is selling them cheap to replace them with E8-130s, so money may be an issue.

and for sheer gas volume, doubling up LP120s and pumping them up to 3800 psi or so can't be beat... most people who aren't cave divers don't need to do this though...

 

[J75]

Jive,

HP steels are small than LP. However, make sure your reg is approved for HP usage, as a HP tank is more likely to cause freeflowing than a LP.

J.

 

[jiveturkey]

Right now I have no use for more air. I run out of no-decompression time before I run out of air. I guess if I decide to take a tech course in the future I might need more air.

Are hp tanks always smaller? Aside from air and size, what other advantages are with the hp tank? What are the differences in buoyancy characteristics that lamont is talking about?

if you have no preexisting preference, going for the LP tanks doesn't seem worth the hassle.

I don't understand. Are hp tanks less hassle? I've never dived the hp tanks so I don't know the benefits. Ignorance is bliss sometimes.

 

[mossym]

well then get some hp tanks, and get nitrox certified..loads of air for more bottom time

hp is always smaller for the same volume of air, you're squeezing the air into a smaller space to create the higher pressure

 

[ColdH20diving]

I have owned both HP and now use LP tanks. I always got a good fill on my HP tanks at my LDS, but not always the case on the road. Have yet to get a short fill on my LP tanks. The smaller size of the HP tanks compared to the LP tank of equal volume is something to consider...

 

[jiveturkey]

The smaller size of the HP tanks compared to the LP tank of equal volume is something to consider...

Why is the smaller tank better?

 

[lamont]

Why is the smaller tank better?

less metal on your back. if you're good with an al80 right now, look into an e7-100 or similar hp100 tank. you should be able to carry a little more gas on your back, in a tank that's roughly the same size and weight, while you take some lead off your weightbelt.

...

as far as buoyancy characterstics go, i wouldn't worry about it. i've used lp104s and e8-130s and while the e8-130s were a bit more head-down than the lp104s, you can move weight around to fix that.

 

[Jawbone]

Let me try to clarify the size diff. between lp and hp. Yes the size of the hp tank is smaller then its lp counterpart at a similar volume of air. For example a lp 95 is the same size as a Hp E8-119. The fill pressure for the hp is 3442 psi. obviously the lp tank fill is significantly lower but most dive stores today can fill to at least 3000 psi. So what this means is even if you get a 3000 psi fill on the hp E8-119 you'll get 109 cubic feet of air or what ever gas your using. Also the hp tank remains slighlty negative at the end of dive as compared to the lp tank which does not. Some divers prefer this such as myself. Hopes this helps. Jason

 

[Jawbone]

Keep in mind the E8-119 is shorter in height than an Al 80. It is also an 8" round tank