Want to buy a tank, but $$$

[Mo2vation]

Cool. Those who have large families (!) or when diving involves a roadie to and from the site, I can understand the trunk full o' tanks.

I'm in neither situation, so having a room full of cylinders is silly.

BUT - I was looking thru my dive log tonight and thinking about this thread, and a light sort of went on. I have some questions - but I don't think about this stuff too much, so use small words in your replies...I think I'm finally getting the LP / HP arguement.

* I dive a PST HP 100. So the only way to really get 100 is to jack this thing up to 3500, right?

* In looking at my log, I'm seeing dive #1 of the day at 3500, 3200, 3125, 3075, etc, etc..(clearly the LDS fills) with the subsequent dives rolling in at 2700, 2500, 2900, etc. (clearly the boat / location fills)

* At 2700 (about the average fill for all dives 2+ for a day) on my HP100, I only have about 77 CU, right?

It looks to me, for these low capacity location "refills" I'd actually do better off with an LP 95, or some other large capacity LP (2700-ish) cylinder.

I've been an HP snob for several years now (and I love the benefits of steel) but it seems to me I may be leaving lots of bottom time on the table with my beloved HP100 when I can only get fills to 77% of capacity.

Did the light go on, or am I on another planet with this?

Thanks -

Ken

 

[RichLockyer]

Mo2vation once bubbled...
What's the deal with the quiver o' tanks?

Throw the three HP120s on my buddy's boat (with his 3) and head out to Catalina. 2-hour bug hunt Friday night, two dives on Farnsworth Saturday, back to the isthmus to refill, then out to SBI for a Saturday night bug dive and two more dives Sunday.

 

[RichLockyer]

Mo2vation once bubbled...
* In looking at my log, I'm seeing dive #1 of the day at 3500, 3200, 3125, 3075, etc, etc..(clearly the LDS fills) with the subsequent dives rolling in at 2700, 2500, 2900, etc. (clearly the boat / location fills)

Depends on the boat, but AFAIK, most in SoCal can't handle more than 3000.
As far as the LDS, the first time my HP120 comes back with 3200 or less would be the last time I get my gas there.

Fortunately, Jim at Scubatoys in Cypress is good, and nails EAN32 within 1/2% and 3500 +/- 100 every time. That's not 3500 +/- when I walk out the door, that's on the boat before I jump in.

 

[scubafanatic]

....you're catching on Mo2vation!

Often the theoretical superiority of HP tanks is negated in the real-world.......that's why I tend to favor LP steels. Boats typically max out at 3000 psi fills, so LP is typically superior for boat trips. Some dive shops and lake/quarry on-site fill stations are lazy and refuse 'custom' fills...they will only do 3000 psi fills no matter what tank you have, as that's the fill pressure for the AL80's/63's the vast majority of the US public dive.

HP tanks can be filled to capacity at SOME of my dive shops/dive sites.......but LP tanks can be filled to capacity at ALL of my dive sites/dive shops.

A few of my LDS's even overfill tanks on request...which is easier to do on LP tanks...however, I've never been to a dive site that will overfill a tank........so if I want maximum fills I'm forced to bring filled tanks with me and not rely on good fills at the dive site.

You're right about the LP 95.....@ 2700 psi it holds 97 cu. ft.....versus the HP 100 holding only 77 cu. ft....so the 'smaller' capacity LP tank holds 26 % more gas.

 

[Atticus]

I went through the same lightbulb process I used to dive HP 100's and loved them. Now I dive LP tanks and typically have more gas.

Welcome to the overfill club (Or not if you're of the conservative nature, but either way LP is the way to go).

 

[Mo2vation]

Do shops get more for selling an HP tank? Meaning, can they get more (sell for a higher retail / and-or margin) for an HP100 than they can for an LP95 or maybe an LP104? Maybe there's no difference - I haven't priced LP Steel v. HP Steel lately.

Side by side, on a shop floor, the choice is a no brainer. The HP's are smaller, lighter, hold more / same volume as an LP (and the shop fills to "3500" and afterall, most of my fills will come from them, so that arguement is diffused) so what's to think about....I'll take the smaller, lighter HP every time.

Don't misunderstand - this isn't shop bashing - let them rock on. I don't want to get into that tired subject. But margin does rule, and I'm wondering if there is a financial incentive to sell HP's, or is it simply the curb appeal that does it?

I'm just thinking that I bought my HP100 without connecting the dots...and now a few years and a hundred-some dives the line, I'm in a dive groove that shows me this probably wasn't the best purchase for my main rig - if only one of 3 fills on each dive is in the 3000+ range and the balance around 2700.

I'm slow, but not 'toopid...Its starting to make sense.

In retrospect, I think the LP104 may be my best bet. I mean, the thing is a hog, but for maximum gas volume on a consistent basis, its probably the best bet. That or one of those fatty LP95's. With most others in my circle diving AL80's or HP100's, I don't want to go nuts with an LP130...as I'll constantly be outlasting the buddy du-jour and coming up to the swimstep with a frustratingly high volume of gas still in the can. You can make the safety margin arguement (can you really have TOO much gas?) I guess.... still thinking about this.

Is there a different type of DIN valve that goes on an HP v. LP? Haven't I read the threading is different? I honestly don't think I've ever seen an LP with a DIN, now that I think about it.

Hmmm....

Thanks -

K

 

[pdoege]

I have LP 104s, LP 120s, and HP 80s.

I love the size and convenience of the HP80s. Perfect for kayak diving.

I have to really watch the HPs like a hawk to get them filled properly. Most compressors are limited to 3500PSI for filling AL tanks. When the HPs cool I wind up with 3200PSI or so.

I normally give the tanks 1 hour to cool and then have the shop top them up. Works if you have the time, doesn't work if you don't.

The LP120s are seriously large tanks! I can move them around without a problem. Many dive shop employees will have problems.

The 104s are smaller, still pretty big.

The LPs always get overfilled. I do not have a problem with that.

In your situation, I would be cool with the HP100s. An AL80 is 77 feet, so you are diving with an AL80 with really good bouyancy characteristics.

I know a diver that uses PST LP85s. Those look to be a really good compromise.

To summarize my thoughts:
1) HP tanks require you to ride the fill station and spend extra time to get good fills.
2) LP tanks are heavier, but you always get good fills
3) HP tanks with good fills are the best, see 1st point.
4) AL tanks are probably not the best, but are ubiquitous.
5) Medium size LPs or the new E8s are probably the best
6) In my opinion, HP80s are the best tank for kayak diving.

Peter

PS. One more thing. If you are already carrying enough air to outlast your buddy, you don't need any more. They are the limiting factor. With a bad fill on my HPs I still have more air than the other divers when we surface. The cranked LP120s are ridiculous. I've ended dives with ~2400 PSI left. Close to the rated fill pressure!

 

[Genesis]

As singles, they are enough for just about any recreational dive - the gas will outlast the NDL, even on "weenie" dives with Nitrox in the tanks.

As doubles, they're still awesome. Still able to be moved around by human beings, but with some effort. Enough gas to do TWO fairly-serious dives and have gas to spare, and if you're a sipper, three or more dives.

I also own a HP120, which is more gas than I need for virtually any single dive. I may sell it.

 

[Mo2vation]

I'm on brain overload right now.

I'm such a geek. I've downloaded the PST sheets, bounced the specs against my logs, weighed the options, calculated the burn rates for my typical dives, etc, etc, etc...

As with LOTS of other stuff in my diving, I'm starting to re-think my cylinder requirements.

When I started, I was a hoover. So I got the HP100, got wifie the HP80 and for a long time, we came up together. Then I started to move into sipper land, and just learned to appreciate the extra 700 - 1200 I'd come up with as emergency gas for her / I.

After reading a few hundred posts today (slow day...can you tell?) I'm loving the E8-130. But unless I'm diving with someone else who's strapped on this waterheater, its silly to cart around the extra weight and gas, only to come up long on every dive. To your point, PDOEGE, a lot of the people I get buddied up with are on AL80's.... Out gassing (I mean seriously outgassing) these people makes little sense.

On most of the boats I dive, I can get up to about 2900 - 3000 if I ride the guys. That still gives me almost 83 - 90 CuFt...not too shabby. Its not 119 CuFt, but the shclep is also about 10 pounds less. Although, I could likely drop 3.5 of that from the belt...

So much to think about. This is why this place rocks. I'm not a doubles guy for the forseeable future, so getting my single dialed in is pretty critical.

It took me awhile, but I need to start to back away from my HP snobbery - the higher capacity LP's make a lot of sense - especially for location and boat fills. I never realized until today how short my second and third dives were, when only getting to 2700, etc. The trade-off for the extra gas is the weight and length.

K

 

[FredT]

Mo2vation once bubbled...
* I dive a PST HP 100. So the only way to really get 100 is to jack this thing up to 3500, right?

* In looking at my log, I'm seeing dive #1 of the day at 3500, 3200, 3125, 3075, etc, etc..(clearly the LDS fills) with the subsequent dives rolling in at 2700, 2500, 2900, etc. (clearly the boat / location fills)

* At 2700 (about the average fill for all dives 2+ for a day) on my HP100, I only have about 77 CU, right?

The internal volume (water capacity) of a HP 100 is not much different from the old steel 72s. 2500-2700 fills were "standard" good fills in them for a long time. (2250 rated+10%approved overfill=2475, most pushed that a bit to about 2700 so they could "cool down." Hydro is at 3750) This worked great if yo didn't leave them in the sun.

Price for a used 72 ready to go is under $50 if you look a bit.

You may want to look at the old SP "blimp" bottles. Those things hold 96 cubic feet at 2400, and really start getting good volume about 3K. Buoyancy is not much off of the 72.

Compare that with the bang for the buck with new HP or even LP tanks if breathing air.

High volume tanks make sense if doing nitrox or tri mix at depth. In the 50 to 90 foot range diving air or low O2 fraction nitrox 72s will generally have you limited by NDT clock, not gas supply.

FT