Should I buy this HP120 doubles setup?

[stuartv]

I've been looking for a pair of HP100 tanks that I can use as singles now and doubles later. I found a set of doubles that turn out to actually be HP120s. I haven't seen them in person yet, but the guy sent me the stamp, which he says is:

DOT-E9791-3500 TP5250

The picture I have looks like they have skinny necks.

I searched around here on SB and found one post that says all E9791 tanks would be 3442, not 3500. I don't have a picture of the stamps on these tanks, just what the seller said they say. Is there something fishy here, or was the post I read wrong?

The seller says he also has the original DIN singles valves for them that he can throw in. I thought that meant I would be good to go, but then I read some other stuff here on SB that said they don't make the valve seats for those any more, so might I be screwed on that, if I buy these? If the singles valves have been sitting around, not on the tanks, for years, am I likely to need new valve seats?

Also from reading here, I gather the singles valves are likely to be Sherwoods that are angled up? Why did they make them that way? I assume that is not as desirable as straight, otherwise that style would not have disappeared into the mists of scuba antiquity. Since these valves are hard to find, am I going to regret it if I end up with tanks with angled valves?

Even if all that adds up and these tanks are good to go (after I get them hydroed - they are out of hydro currently), am I making a mistake to buy HP120s? Should I just hold out for 100s?

I am only OW and basic Nitrox certified at this point. So, I realize that 120s are probably overkill for my current single tank diving. My RMV, so far, has been running .55 - .65 cuft/min. Not great, but probably (haven't actually run the numbers) good enough that 100s would let me stay down for as long as my NDL would, even on Nitrox. Or at least close to it. And I'm hopeful it will improve some as I get more experience.

But, my sights are set on progressing through, eventually, Adv Nitrox and Deco Procedures. At that point, it seems like having 120s might be really nice.

OTOH, I have read a number of posts that say the extra 4" height of the 120, versus the 100, might make them uncomfortably tall. Does that really affect anything more than sitting down in front of it and getting into my rig? Does the extra length have any real impact when I'm in the water?

I am 6' 1", with a 32" inseam (so, I think, a torso on the long side of normal for my height).

I feel like I need the top of the tank in the same place, no matter the length. Lower, and I can't reach the valve behind me. Higher, and I hit my head on the first stage. So, the extra length will just hang down my back that much further. Is that going to affect my ability to trim out properly?

The buoyancy looks pretty similar to the 100. Same when empty. 1.5# more negative when full. That seems like no big deal.

In the end, even if they are not ideal, as long as they will be usable as singles without causing me much issue in the water, I feel like I should go ahead and get them. I think the price is right and I really want tanks of my own before my upcoming training dives in June. If it turns out I'd be better off with 100s, hopefully I'll eventually be able to sell or trade them at some point to turn them into 100s. I go down to FL several times a year to visit family and I read that these HP120s are popular among cavers down there.

Any info or advice any of you can impart would be truly appreciated!

 

[lv2dive]

Honestly, if I had that many questions about a gear purchase I would walk away.

I don't mean that as a statement of judgement I mean it as statement of fact.

 

[stuartv]

If I took that tack, I wouldn't currently own any scuba gear at all. The cost on pretty much all this stuff is high enough - to me - that I want to research things as thoroughly as I can before forking out cash.

They're scuba tanks that look in decent shape. I could just go buy them without even contemplating all these questions. It COULD be that simple. But, I don't want to do that and then find out the hard (expensive) way that, woops, I'm not really going to be able to convert them for singles use. Or, woops, these things are going to so hard for me to trim out that I'm going to wish I never bought them.

I hate being the "dummy! You should have checked into that before you bought it" guy!

 

[Lorenzoid]

Can you rent some different tanks and see what works best for you? Why buy used gear only to later wish you had forked out a little more for the RIGHT item?

 

[tbone1004]

per pm I say yes, but to answer your last question.

You can convert them to singles use, not using the valves that are on there, but using the singles valves he has agreed to provide, they are quite easy to convert. Adjustable wrench and a pair of jar lid opening pads are all you need.

They will trim out fine, the only length issue will be your ability to comfortable sit depending on your circumstances, for non boat use they'll be fine, for boat use I dive with a bunch of guys your height with 120's and they love them, but with a properly adjusted one piece harness, there is plenty of slack to sit down as long as the crotch strap isn't too tight. For $400 if you don't like them, you can always sell them for that price.

 

[stuartv]

Can you rent some different tanks and see what works best for you? Why buy used gear only to later wish you had forked out a little more for the RIGHT item?

I don't know if I can rent HP120s anywhere around here. But, my general philosophy is, why pay to rent something if I can buy it used for a sufficiently good deal? If I can buy it, try it, and flip it for what I paid, then renting is wasted money. If I try it and like it, then I'm all good. And I wouldn't be buying it if I didn't at least THINK I would like it. So, the only real gamble is if I thought wrong, then I'm potentially out just the hassle of selling it after I try it.

I have done this a lot with bass guitars. You can never say for sure how you'll do on any one thing you try. But, over the course of trying a lot of different stuff, I have proven to be a good enough shopper to average a small profit on these things.

per pm I say yes, but to answer your last question.

You can convert them to singles use, not using the valves that are on there, but using the singles valves he has agreed to provide, they are quite easy to convert. Adjustable wrench and a pair of jar lid opening pads are all you need.

They will trim out fine, the only length issue will be your ability to comfortable sit depending on your circumstances, for non boat use they'll be fine, for boat use I dive with a bunch of guys your height with 120's and they love them, but with a properly adjusted one piece harness, there is plenty of slack to sit down as long as the crotch strap isn't too tight. For $400 if you don't like them, you can always sell them for that price.

Awesome, got your PM, too. Thanks again! I'm on it.

 

[jcaplins]

The tanks should be similar in height to AL80's. I've used rental hp120's for NC and VA diving, and I loved 'em. I'm 6' with something like 30 or 32" inseam.
If you separate the tanks, you should be able to use the existing valves, just remove the isolation manifold and install plugs.

 

[stuartv]

I've let the seller know that I am a definite on taking them.

I will have to take them in for a hydro and VIP.

Is it expected that I could take them to the shop as an assembled doubles unit and they will break it down and put it back together as part of the process?

Assuming so, would it then be reasonable for me to take the singles valves with me and ask them to reassemble them as singles, instead of putting them back together as doubles?

Should I expect that they would charge me something extra for any of that?

Sweet!! If this all comes off as planned, I will shortly have my very own AL30, HP100 and 2 x HP120s! Being able to go diving whenever I want, with the only expenses being $5 air fills (or $8.50 for Nitrox at my LDS) is very exciting!

 

[jcaplins]

Is it expected that I could take them to the shop as an assembled doubles unit and they will break it down and put it back together as part of the process?

yes

Assuming so, would it then be reasonable for me to take the singles valves with me and ask them to reassemble them as singles, instead of putting them back together as doubles?

yes

Should I expect that they would charge me something extra for any of that?

Yes. maybe $20(?).

You could do it yourself. Here's how to put them together: https://www.youtube.com/watch?v=7Iv-xtPWFdA
Just watch the video backwards to disassemble :cool2:

 

[tbone1004]

jcaplins, they are a full 2 inches taller than an AL80 which is actually pretty significant, they dive very different on your back. If you looked the link, the manifold is the Sherwood isolation manifold which can't be plugged, have to use different valves.

regarding hydro, I wouldn't go to an LDS for the hydro, try to find the hydro shops in your area and take them directly there. I would disassemble them yourself first, bleeding them down pretty slowly to avoid condensation then put the singles valves in yourself with the tanks empty and take them to the hydro shop. Quite a few will actually have a VIP sticker to put on there for an extra $5 since it is federal law that a full visual inspection be performed prior to putting it in the dunk tank for hydro. We get ours for about $20 for hydro and vip, no fill obviously but they sometimes have adapters to put a few pounds in there to keep them sealed.