# Question of LP and HP tanks



## BOHUNTER1 (Feb 18, 2008)

Im asking because it doesnt make sense to me!

OK. I have a few buddies who I ask for pointers from and then again Ive heard a few on here and others who have mentioned their opinions of HP vs LP tanks...

NOW... If you tank the Valve off a tank its a Cylinder with a threaded hole and empty / hollow correct?

Does the Valve make it LP/HP or just someone tell me what the difference of an LP 85-119 or a HP 80 - 120........ If the LP can be overfilled wouldnt this be freaking HP or the same pressure as a HP tank filled cylinder? Its late and Im thinking ...or I have 1 Atm Narcosis tonight? I dont understand the pressure of the tanks I guess....???? Hmmmmmmmmmm Maybe it was my training from MBT that has gotten me into this, who knows.....

Someone explain the difference of the LP and HPtanks.

Appreciate the help.

Steve Holloway


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## FelixH (Sep 28, 2007)

Everyone talks about overfilling the LP tanks. And many of us do endorse it. But, technicaly, unless your LP tank has a "+" rating, you're not supposed to fill it beyond the stamped working pressure. If it says 2400, then it's supposed to be filled to 2400. End of story.

Ifit's a 2400psi rated tank with a "+" rating, then it can be filled to 2400 + 10%, for a total of 2640psi.

But, yes, overfilling the LP tanks is kind of a common practice.


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## Brandy (Sep 28, 2007)

what makes it high or low pressure is the type of steel its made of. A HP tank is made of better steel or aluminum whichallows more pressure. With more pressure you can cram more air into a smaller package. So A HP 100 is smaller size than A LP 95. Valves are A little different too. Some valves are only rated to 3000psi and some are 5000. I dont know if the housing of the valve is any different but the burst disk definatley is. Low pressure is usually the way to go. If you get A LP fill you have all yourair as rated. If you get an overfill to 3000psi you get quite a bit more air than rated. You can go over to cave country and get a LP pumped up to almost 4000 psiand almost double rated air. 

I hope I told you right.


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## sealark (Sep 27, 2007)

That 10% overfill on steel tanks is only good up to the first hydro. Your HP tanks are made from the same steel just lift a HP and then an LP of the same physical height and width and you will see why they have a higher pressure rating way to heavy for my old ass. The HPs are just thicker material. Also some of the threads on the HPs are different and smallerthan the standard 3/4" NPS threads on the LPs.


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## BOHUNTER1 (Feb 18, 2008)

Thanks guys!

Just been curious. Ill stick to AL80's I guess.


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## JSeaWach (Oct 29, 2007)

Don't forget buoyancy characteristics...With a 3mil wetsuit and 5 lb. back plate, I carry zeroweights when diving either LP95 or HP120. With an aluminum 80 I have to carry 6 additional pounds. Makes me feel like a skinny teenager again! :toast


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