HIGH PRESSURE TANK vs LOW PRESSURE TANKS...?

[eelnoraa]

Maybe it is a regional thing, here in US, HP tank is 3442psi. Yoke connection Will work just fine. I have been using Yoke on HP100 for a couple of years.

As for lp vs HP tank, I will say go with HP tanks. Most lds should be able to give you good fill these days. The only exception I have seen is on a mobile fill station, such as on a dive boat. And even you only get 3000 on HP100, that is still 90 cf. Overfilling lp tank is nice if you are sure you can get that.

---------- Post added May 7th, 2013 at 09:33 AM ----------

The less added weight with steel is a bonus.

Assuming you need the weight, steel not only means less added weight, but less overall dry weight. The later makes carrying your rig (entry/exit) easier.


On the other hand, if you don't need the weight, steel can make you over weight.

 

[kaerius]

European HP tanks are made with DIN regs in mind and go to 300 BAR/4350 PSI as working pressure(and typically have an actual max fill pressure of about 330 BAR/4786 PSI).

I have a 10L such at home, barely used as I don't dive much in the cold swedish waters, there's just not so much interesting to see to justify being cold(I don't have a drysuit, but even with that, the cold bites your face). I might give a local river a go in late summer for a drift dive, we'll see. If I'm lucky the water temp goes up to 15°C/59°F.

 

[50Fathom]

I prefer LP tanks, not only for the fill advantages, but I seem to trim better in them, thanks to that extra 1-1.5" of length. It balances me better front to rear. I don't know why such a little bit makes a difference, but I've dialed myself in to the point that I can feel it.

(All tanks referenced are new Worthingtons.)

HP100s make me head heavy, but LP85s balance perfectly. (My favorite GP steel tank)
HP130s trim me head-heavy, but LP108s are, again, perfect.

The exception seems to be the old 2250 72s. I can trim those out all sexy-like, regardless of manufacturer, (I hear tell the different brands, though the same size, had different buoyancy and trim characteristics.)

For example, I can dive HP100s, but I'm working harder than I want to to stay perfectly flat. And my 85s, when pumped to 3442, hold 105cft. So I get better trim, a slightly more gas? Win.

Yes, I have access to a compressor, and no, I never fill a steel tank below 3200 cool. (Provided the burst disks are upgraded or doubled-up.) Anything less is a waste.

 

[Dr. Lecter]

Let me rephrase: To fully utilize the higher pressure rating of a HP tank you need to have a DIN reg, period. If you're filling a 300BAR/4350 PSI tank with 241BAR/3500 PSI, because that's all your yoke can handle, you're only using 80% of its capacity.

True enough. And maybe you guys have those over in Sweden... but 3442/3500psi are the only remotely common HP tanks here in the US.

 

[HIGHwing]

I doubt you'll see much of that with LP tanks, considering that it's approaching their hydro test pressure.

You can doubt if you wish, but everyone's already told you the assumption you've made is not coincident with how low pressure tanks are used in practice. We generally turn the dive when the tanks are full, and that works out just fine.

 

[elmer fudd]

You can doubt if you wish, but everyone's already told you the assumption you've made is not coincident with how low pressure tanks are used in practice. We generally turn the dive when the tanks are full, and that works out just fine.

What hard core divers can do and what beginning divers outside of cave country have access to are completely different things. The OP is a new diver living in Los Angeles. Saying, "we fill our tanks this way all the time", means nothing if you live somewhere where they won't do it for you. I'd be very surprised if a beginning diver here on the west coast were getting 4000 psi fills on their LP tanks.

Everyone has heard of cave fills before, heard the turnaround pressure joke and no one doubts that you can put a lot of air into an LP tank, but if an unknown diver showed up at a shop around here expecting a cave fill on their LP cylinder, my guess is they'd probably be shown the door.