twin LP72s

[jcaplins]

Looking for advice and things to consider....

I'm thinking of picking up a couple of used steel LP72's.
I believe I can get 2 with fresh Hydro for $75 each.
I would still need valves w/ isolation manifold and bands.
- convertible valves (for DIN use) and a manifold with 215mm spacing
- Bands need to be for 6.9 inch diameter tanks.
(correct?)


Right now I want to develop the practice, experience and consistency of using doubles, without killing my self hauling these things around. I'm typically doing recreational shore diving in California.

The reason for the twin 72's is to have/use doubles and the weight. I have a pair of HP100 tanks and they are great as singles and god awful heavy as doubles for the diving I'm doing now. (I would love to have a pair of Faber LP50's, but the availability and cost is not good.)

1st: how heavy are these things, really?
2nd: Are they worth it for the mission I've described? would you suggest something else, instead?
3rd: If I hate them as a twin setup, do they work well for sidemount, stage, deco, pony bottles?

What should I look out for in a used LP72? (lining, age, etc.)
Let me know if I've got anything wrong.

who wants to sell me some valves/manifold and bands?


Thanks in advance for your feedback,

 

[rjack321]

1st: how heavy are these things, really?

steel 72 = 26lbs empty
hp100 an exemption tank not a 3AA = 34lbs

So doubled the 72 are about 60lbs plus 12lbs of air = 72lbs
the 100s are 68 + 14lbs of gas (assuming air) = 83lbs

the 11lbs is pretty significant in surf or if there's a long walk. I would stick to singles for shore dives and use the doubles on charters

2nd: Are they worth it for the mission I've described? would you suggest something else, instead?

72s are really the only doubled tanks which will actually act like doubles, eg doubled lp45s would defeat the point of practicing with doubles

3rd: If I hate them as a twin setup, do they work well for sidemount, stage, deco, pony bottles?

They make great shore diving singles at those large shallow beach sites in CA

What should I look out for in a used LP72? (lining, age, etc.)

3/4" Oring sealed valves, not 1/2" taper thread
NO vinyl linings or exterior coatings, the lining can sometimes be removed with really aggressive tumbling. But you might find pitting underneath after all that work. The vinyl outer coating is just a disaster, pass on those and find some hot dipped galvanized ones.

 

[scubastingray]

steel 72 = 26lbs empty
hp100 an exemption tank not a 3AA = 34lbs

So doubled the 72 are about 60lbs plus 12lbs of air = 72lbs
the 100s are 68 + 14lbs of gas (assuming air) = 83lbs

26*2=52, 52+12=64, 64vs 83 lbs is a lot larger difference.

 

[halocline]

I used double 72s for a good long time to practice getting the hang of doubles. I found them to be great starter doubles, although I recently broke up the set and built a set of AL80 doubles, which I was surprised to find better for trim and stability. I didn't expect that because the single 72s are SO much better than single 80s IMO.

Anyhow, you do need 7" bands or vintage style 6.9" bands. The 7" bands are pretty easy to find. I just used a standard manifold, the spacing is adjustable; you thread the cross bar together with the valves and as long as there are not more than the maximum number of exposed threads (as recommended by the manifold manufacturer) it's fine.

As far as the tanks go, try to find PST galvanized. They are usually painted over the galvanizing, but it's easy to take that paint off and either leave the galvanized finish alone or touch it up with ZRC galvilite. The reason I like PST 72s is that there is a document floating around the net that has the PST REE values, and you do have a reasonable chance of getting the plus rating on the tanks. This gives you a working pressure of 2475 and 71.2 cft. Without the plus, they only hold about 65 cft.

Carrying the AL80s is a bit more work, and you need to carry a little more lead, but as I mentioned, for me they do trim out better. I switched because AL80 doubles is what you get in MX cave systems, and I wanted to practice with the same tanks I'll be using there. But it is another option for cheap, relatively easy-to-manage doubles.

 

[scubastingray]

How would you check to see what brand the tank is?
I have one that is marked with US divers/aqua lung and is DOT 3AA2250, HJ 306793 USD made in 73. It was originally + rated and I've been holding off on getting it hydro'd again until I could get the +. I found the shop but assume I'll need to provide the REE values.

Sorry to thread jack, but it's related to LP72s and I have an old one that has been sitting for a few months.

 

[jcaplins]

Thanks everyone. I picked up 2 tanks, hot dipped galvanized, hydo'ed just recently, 3/4" o-ring sealed valves. All looks good. One is a 1960, the other 1964. Neither are supposed to have an inner liner. I've got some old bands as well.

I could use them as independent doubles right now, but I would still like to find a 200 bar, convertible, isolation manifold/valve set.

 

[scubastingray]

What type of spacing do you have on your bands? This is certainly a cheap way to setup a doubles manifold if it will fit:
DGX Premium Cylinder Valves - Dive Gear Express (the $100 doubles manifold & valves).

 

[halocline]

How would you check to see what brand the tank is?
I have one that is marked with US divers/aqua lung and is DOT 3AA2250, HJ 306793 USD made in 73. It was originally + rated and I've been holding off on getting it hydro'd again until I could get the +. I found the shop but assume I'll need to provide the REE values.

Sorry to thread jack, but it's related to LP72s and I have an old one that has been sitting for a few months.

Mine have PST stamped on the tank, along with the distributor USD. There are only a few manufacturers, PST, Walter Kidde, Norris, I forget if there's anyone else that made 72s. Look for the first hydro mark, you might find a K in a circle, or a N in a diamond, or a C which is Cochran labs that did the hydros for PST (I think). There are good threads about this fairly recently with much more thorough explanations; look for a post by herman.

I'm having trouble finding a place in San Antonio that will do the plus rating, I had a disaster with one hydro shop, I'm getting utter BS from another. Eventually a buddy found a shop in austin that apparently will do it. It's AMAZING to me how these guys all claim they know the rules and they're all different.

---------- Post added April 6th, 2014 at 09:10 AM ----------

I could use them as independent doubles right now, but I would still like to find a 200 bar, convertible, isolation manifold/valve set.

Manifolds are all over the place. I got mine at piranha dive gear. With the current sidemount craze, there should be plenty of manifolds for sale. Another place would be north east scuba supply, look at their used inventory.

 

[Stoo]

My first doubles were 72s and I still miss them... Just be sure to have them visualled and Hydro'd if they're ancient. (Mine eventually had to be condemned... they make awesome doorbells in their afterlife...)

I replaced them with LP 80s and they behave in about the same way, and aren't much heavier. I also have 95s and 130s, but the 80s are my favorites...

 

[scubastingray]

Mine have PST stamped on the tank, along with the distributor USD. There are only a few manufacturers, PST, Walter Kidde, Norris, I forget if there's anyone else that made 72s. Look for the first hydro mark, you might find a K in a circle, or a N in a diamond, or a C which is Cochran labs that did the hydros for PST (I think). There are good threads about this fairly recently with much more thorough explanations; look for a post by herman.

I'm having trouble finding a place in San Antonio that will do the plus rating, I had a disaster with one hydro shop, I'm getting utter BS from another. Eventually a buddy found a shop in austin that apparently will do it. It's AMAZING to me how these guys all claim they know the rules and they're all different.

Okay, mine has an N in a diamond, so it's a norris tank? Damn this will make the plus rating difficult.

I know a fairly reasonable fire testing shop that I think I can get to do the + rating. I just don't want to have a 65cu ft tank.