LP vs HP Tanks
- Thread starter rstofer
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I appreciate all the responses so far. I should have further limited my question. I have 6 HP-100s, 2 Al 80's, 5 Al 50's (for my grandson) and that steel 72. Cost is not a consideration. I already have enough tanks but, since there is still a little more room under my work table, I could still buy more.
It is true that for the types of diving we are doing today, the HP 100 has too much air. My grandson is limited to 40' (my view is it should be 30') and he is using 50 cf tanks. So, we tend to use just a little more than half a tank per dive. But I don't know that it would be worth buying LP80s to just reduce weight by 3#.
The Worthington X-7 HP 80 would drop 5# without making a huge change in buoyancy. But it's hard to justify if we're only talking about the cost of air being left in the tank. Still, it would be easier on my back.
Thanks!
Richard
It is true that for the types of diving we are doing today, the HP 100 has too much air. My grandson is limited to 40' (my view is it should be 30') and he is using 50 cf tanks. So, we tend to use just a little more than half a tank per dive. But I don't know that it would be worth buying LP80s to just reduce weight by 3#.
The Worthington X-7 HP 80 would drop 5# without making a huge change in buoyancy. But it's hard to justify if we're only talking about the cost of air being left in the tank. Still, it would be easier on my back.
Thanks!
Richard
Scared Silly
Contributor
There is a lot to be said for easier on the back. That was one of the decisions that went into some recent cylinders purchases - not just between LP and HP but between mfgs. As such, it is necessary to take into account both the buoyancy and dry weight into consideration.
Scared Silly
Contributor
just the amount gas not the pressure it is stored under as that is what a regulator is for.
As I said, I have been of the opinion that, without overfills, there is no purpose served by LP tanks. That's a pretty extreme position and, no doubt, I am wrong. I'm looking for enlightenment. There's a reason the tanks are manufactured.
Cubic feet are cubic feet, it doesn't make any difference what pressure is in the tank except for its effect on the regulator. In terms of double hose regulators, the yokes may not really be designed for 3442 psi. Some double hose regulators breathe worse at high pressure than low. They tend to work best around 1800 psi or so. That doesn't apply to modern single hose regulators.
There are those that suggest that high pressure tends to wear the high pressure seat in the first stage faster than low pressure. What do I know about regulators? They're probably right. But I get the regulators serviced every year. Let the tech deal with it.
For a given capacity in cubic feet, LP tanks will be larger and heavier than HP tanks. OTOH, they will be easier to fill. That doesn't matter to me becuase I leave them at the shop until they are full. I don't see a situation where they would be filled somewhere else.
If I have to have tanks filled elsewhere (an overnight trip out of the area), I rent tanks. I don't want to contaminate my Nitrox tanks and have to have them recleaned.
But there are some knowledgeable folks on this forum and if there is a specific application for LP tanks, I want to know about it.
I'm not in the market for tanks at the moment but I want to at least have a reason for what I purchase in the future.
Richard
Cubic feet are cubic feet, it doesn't make any difference what pressure is in the tank except for its effect on the regulator. In terms of double hose regulators, the yokes may not really be designed for 3442 psi. Some double hose regulators breathe worse at high pressure than low. They tend to work best around 1800 psi or so. That doesn't apply to modern single hose regulators.
There are those that suggest that high pressure tends to wear the high pressure seat in the first stage faster than low pressure. What do I know about regulators? They're probably right. But I get the regulators serviced every year. Let the tech deal with it.
For a given capacity in cubic feet, LP tanks will be larger and heavier than HP tanks. OTOH, they will be easier to fill. That doesn't matter to me becuase I leave them at the shop until they are full. I don't see a situation where they would be filled somewhere else.
If I have to have tanks filled elsewhere (an overnight trip out of the area), I rent tanks. I don't want to contaminate my Nitrox tanks and have to have them recleaned.
But there are some knowledgeable folks on this forum and if there is a specific application for LP tanks, I want to know about it.
I'm not in the market for tanks at the moment but I want to at least have a reason for what I purchase in the future.
Richard
It almost looks like you just spent the last post outlining any advantages given, and then shooting them down because you have specific workarounds. Then you again ask if there are any applications for LP tanks, suggesting that such advantages don't apply generally. I think the short answer is, for your needs, HPs are just perfect, and there are no advantages to LP tanks. Just stick with the HPs and enjoy the fat fills.
Well, you brought up nitrox. If you're mixing at home, the lower pressure of the LP tank helps use more oxygen from your source tank (assuming you don't have a booster at home).
Second, and this issue was a real problem with a friend of mine last year, is that the HP tanks are usually NOT 3AA tanks and are more prone to fail hydro. My friend had 3 out of 4 PST HP100's fail hydro. (And yes, this hydro shop was familiar with the trickery spelled out in the PST bulletin).
Faber makes some mid pressure tanks (3498 psi with the plus rating, 3180 without) that are 3AA tanks, but unless you're diving with a lot of lead, you probably won't like them as they're about 15 lbs negative, full (for the 100 cu ft tank). Personally, I dive cold water and love them.
You could also let your grandson dive with the AL80's and save money on fills, as he'd be able to do two dives on one fill.
Second, and this issue was a real problem with a friend of mine last year, is that the HP tanks are usually NOT 3AA tanks and are more prone to fail hydro. My friend had 3 out of 4 PST HP100's fail hydro. (And yes, this hydro shop was familiar with the trickery spelled out in the PST bulletin).
Faber makes some mid pressure tanks (3498 psi with the plus rating, 3180 without) that are 3AA tanks, but unless you're diving with a lot of lead, you probably won't like them as they're about 15 lbs negative, full (for the 100 cu ft tank). Personally, I dive cold water and love them.
You could also let your grandson dive with the AL80's and save money on fills, as he'd be able to do two dives on one fill.
It almost looks like you just spent the last post outlining any advantages given, and then shooting them down because you have specific workarounds. Then you again ask if there are any applications for LP tanks, suggesting that such advantages don't apply generally. I think the short answer is, for your needs, HPs are just perfect, and there are no advantages to LP tanks. Just stick with the HPs and enjoy the fat fills.
This is very probably the case. For what I do, the HP 100s are pretty good.
Still, there is the matter of those 3 double hose regulators that would prefer a lower pressure. For no other reason, I may still buy a pair of LP tanks.
I'm really just looking for a good excuse to buy a couple. Maybe the double hose bit is enough.
Richard
I think the Al 80s are a little heavy for him right now. He just turned 11.
I have been thinking about some HP 80s that might work out pretty well. I have to think about it. If he gets signed up for Peak Performance Buoyancy, I want to get rid of the aluminum tanks.
I'll keep the 50s for the pool. They are excellent for that application. I also have a doubles manifold and a set of retro bands that fit these tanks.
Richard
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