MrPfeffer
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Excuse my ignorance on this but why go with lp tanks over a hp tank? Is there an advantage to using LP tanks? better for doubles?
hp vs lp
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spoolin01
Contributor
No excuse needed, it's a favorite optimality topic. I switched from HP120 to LP120 because I wanted 120 fills but couldn't get them at any of 3 local dive shops with the HP tank. Also, a bit easier on the compressor if you fill your own, and you can top them off to the pressure you want, should you get a hasty and lazy LDS fill, if you keep a full HP tank and transfer whip around.
If not for the fill issue, I'd rather use HPs for their lighter weight and negative bouyancy when (almost) empty. When I travel and want to save space or weight, I take HP100s and resign myself to diving half the time with barely 80 cu ft.
If not for the fill issue, I'd rather use HPs for their lighter weight and negative bouyancy when (almost) empty. When I travel and want to save space or weight, I take HP100s and resign myself to diving half the time with barely 80 cu ft.
eelnoraa
Contributor
I don't think valve type has anythign to do with choosing LP or HP. Locally, I see a lot of tech diver prefer LP tanks for their double setup. From what I understand, it comes down to 2 reason: 1) LP tanks are more likely to be neutral empty, and HPs are more negative. You can actually be too heavy even with drysuit. It all come down to "balance rig". Although more lead may be needed. These lead can be used for better weight distribution and/or as ditchable weight. 2)LP tanks have better tank factor than HP tanks, so if over filled, there are potentially more air in them. These are just my observations.
Chugwhump
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I dive them all.
What do I know?
Chug
Changes weight as required.
What do I know?
Chug
Changes weight as required.
decidedlyodd
Contributor
It's basically a set of tradeoffs.
LP Advantages: Cheaper, easier to get a good fill in some places
HP Advantages: Smaller size and weight relative to the amount of air held
I ended up going with HP tanks myself because it's no problem around here to get a good fill on HP tanks.
LP Advantages: Cheaper, easier to get a good fill in some places
HP Advantages: Smaller size and weight relative to the amount of air held
I ended up going with HP tanks myself because it's no problem around here to get a good fill on HP tanks.
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MrPfeffer
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Ive seen a few lp tanks for sale recently in my area and was wondering if it would be worth getting, since Ive been in the market for tanks, or just go for the hp tanks. I only rent hp tanks from my local shop currently and fills are always pretty good. Didnt realize the neutral bouyancy thing that might be worth looking into some more. Thanks all for giving me some insight
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Take a look at this chart:
http://www.nwscuba.org/resources/rec-diving/Scuba Tanks and Buoyancy.pdf
A HP119 is roughly the same size as a LP95. They are basically the same size and have pretty much the same buoyancy characteristics with the HP119 being slightly more negative when full and slightly more positive when empty due to the extra gas.
If you fill that HP119 to 3000 is holds 103cf. While you may run into places that can't fill all the way to 3442, because of the popularity of the AL80 with a fill pressure of 3000, it would be unusual to not be able to get a fill of at least 3000.
So, for the same size and weight, you get more gas even on a short fill, and if you can get a full fill you get even more. Many will say, well, I'll just cave fill the LPs, which I can't understand when there are tanks rated for higher pressures that are otherwise almost the same. Why not just get the ones rated for higher pressures? Based on this reasoning, all my tanks are high pressure steel.
http://www.nwscuba.org/resources/rec-diving/Scuba Tanks and Buoyancy.pdf
A HP119 is roughly the same size as a LP95. They are basically the same size and have pretty much the same buoyancy characteristics with the HP119 being slightly more negative when full and slightly more positive when empty due to the extra gas.
If you fill that HP119 to 3000 is holds 103cf. While you may run into places that can't fill all the way to 3442, because of the popularity of the AL80 with a fill pressure of 3000, it would be unusual to not be able to get a fill of at least 3000.
So, for the same size and weight, you get more gas even on a short fill, and if you can get a full fill you get even more. Many will say, well, I'll just cave fill the LPs, which I can't understand when there are tanks rated for higher pressures that are otherwise almost the same. Why not just get the ones rated for higher pressures? Based on this reasoning, all my tanks are high pressure steel.
FWADIVER
Contributor
several reasons, first of which is buoyancy characteristics. Second of which is you can overfill a lot higher than 3500 with a lp steel if you need it.
Ok, bare in mind that this is location dependant. This doesn't work everywhere. But, lets take N. Florida.
In every way but LP is better. Here's why.
LP is cheaper
LP has better bouyancy characteristics
LP holds more air when overfilled
LP has been around for 40+ years and is very stable (tried and true).
So, lets look at some math...
An LP85 holds 85cu' of air at 2640. But if you fill it to 3600 it holds 116cu'. That's 116cu' of air in the tank the size of an AL80. And shed some lead getting into the water. What's an HP100 hold at 3600? Answer: 105cu'
An LP95 holds 95cu' of air at 2640. But if you fill it to 3600 it holds 130cu'. If you fill it to 4k (which is very common for the past 2 decades in N. Florida) it holds 144cu' of air. Lets see an HP119 due that. HP119 at 3442 = 119, at 3600 = 124cu' and at 4k (if you're dumb enough to do that) = 138cu' of air.
LP tanks have been around for decades. There has never been a scuba related fatality from overfilling an LP tank. HP tanks haven't been around long enough to know what's going to happen at repeated fills to 4k. Time will tell. For now, I'll stick with what is known. LP is cheaper, LP has better buoyancy characteristics (for me), LP holds more air, and LP are tried and true.
In every way but LP is better. Here's why.
LP is cheaper
LP has better bouyancy characteristics
LP holds more air when overfilled
LP has been around for 40+ years and is very stable (tried and true).
So, lets look at some math...
An LP85 holds 85cu' of air at 2640. But if you fill it to 3600 it holds 116cu'. That's 116cu' of air in the tank the size of an AL80. And shed some lead getting into the water. What's an HP100 hold at 3600? Answer: 105cu'
An LP95 holds 95cu' of air at 2640. But if you fill it to 3600 it holds 130cu'. If you fill it to 4k (which is very common for the past 2 decades in N. Florida) it holds 144cu' of air. Lets see an HP119 due that. HP119 at 3442 = 119, at 3600 = 124cu' and at 4k (if you're dumb enough to do that) = 138cu' of air.
LP tanks have been around for decades. There has never been a scuba related fatality from overfilling an LP tank. HP tanks haven't been around long enough to know what's going to happen at repeated fills to 4k. Time will tell. For now, I'll stick with what is known. LP is cheaper, LP has better buoyancy characteristics (for me), LP holds more air, and LP are tried and true.
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