72's Scuba Tanks

[LadyDiva]

Purchased some used steel 72's and then dropped off the tanks at the LDS for vis & hydro (last hydro'ed 10 years ago). I don't have the tank details, but think they were mfg. in the 1970's.

Unfortunately, the LDS says they need to be tumbled because they have an interior lining. I bought them for $30 each and it will take another $90 to tumble, hydro, vis & replace the old J-valves with K-valves.

Questions.... Is it worth it, $120 total for each tank?
Or should I take the LDS offer to buy them for $20 each?
Or should I try to tumble them on my own and look for some used K-valves?
What is "too" much to spend on these tanks?

Note, I prefer steel tanks over aluminum, so if I had the choice, I'd buy a used steel tank for price of a new alum tank.

 

[Rich Keller]

You do not need to tumble the tank unless the interior lining is bad. If the lining is in perfect condition then take it to another shop. These tanks will pass hydro and VIP with the lining in place.

 

[SOFDiver]

Considering the price of new/used steel tanks $120 does not seem to be a bad deal as a total investment. Dispite suggestion above, as last hydro was 10 years ago and history of tanks is really unknown, tumbling the tanks is also worthwhile. I too think tanks will pass hydro, and if they were mine I would want to know that they were 100% before I put them into service. I also submitt that your LDS really has no real intrest in steering you wrong about tumbling, the process takes a lot of work and there is very little profit after time/effort is considered. Done a few myself, and don't suggest it to customers unless necessary for safety.

 

[spectrum]

Getting into steel 72's for ~$120. a good deal, not a steal but still very cost effective.

I can't say on tumbling the lining, there were several forms.

Immediate replacement of the valves may not be essential. Most J's can still be used. Some knobs are nasty to work and may be candidates for immdiate replacemnt.

Are these all standard 3/4 thread? Otherwise valve options get slim.

Are they hot dipped galvanized? Painted steels can get ugly, especialy under the boot. Check under there and be sure to have good self draining boots. The old clingy ones are big trouble. New boots, $12. or so, Trident has them, any sop can procure.

If hot dipped galvanized be sure they follow the rounding out procedure at hydro.

Do you or the shop have the REE number(s) for the cylinder models in question so you can explicitly request the + rating? If no, do some research beforehand.

Pete

 

[oldschoolto]

If hot dipped galvanized be sure they follow the rounding out procedure at hydro.

Pete

Can you tell me what that is....

jim

 

[Gilldiver]

With a liner they are most likely made between 1969 and 1972. The liners came in a light cream color and a dark red or brick color. As long as the liner is in good shape and not flaking it should be good to go. The hazard is that there may be some rust pitting under the liner that you need to look carefully for. When in doubt I will use a tank whip for a minute or so, if there is a rust bubble the whip should break it open and give an indication that liner removal may be required. To remove the liner you need to use a cutting media that will bite into the liner as standard media used for normal tumbles will take a long time (days) to ware down the liner. One media that has been used is a few pounds of deck or dry wall screws. Even with the screws you need to tip the tank to get all of the bottom and neck. An alternative is shot/sand/grit blasting, some Hydro place can do this but you have to call around to find one.

Generally I would pay around $60 for a steel 72 with a 3/4" valve and once got 3 for $50, (even pulled 2 out of the metals pile at my local transfer station and each had over 500 psi in them) and take my chance which is small that they will not fail a hydro.

As for valves, valves are cheep and if you ask around a few shops one or two may let you have some from condemned tanks for free or a few dollars.

Once you are through hydro you will have a tank that with proper care, can be used by you grand and great grand children.

 

[captain]

Roundout procedure

 

[DA Aquamaster]

I disagree with some of the advice given here. Current tank liners are usually white, smooth and comparatively thin, so any rust that may be starting under a pin hole becomes very obvious due to stains under the liner and a no longer smooth surface.

The liners used in the past by US Divers and other companies was darker in color and usually much rougher surfaced. That made any staining around a pin hole very difficult to see and any bulging from rust underneath much less noticeable.

The critical issue is whether the coating could be concealing rust underneath and the rust in a pin hole in a well adhered liner material can quickly result in a pit that can be hard to see in the older, rougher and darker liner materials. I would in no way shape or form pass a tank with the older liners on a VIP and I'd bet the majority of VIP inspectors would agree - especially if they are also the people who will be filing the tank for the next year.

Using a whip on a liner is counter productive. You may well loosen loose areas of liner, but you also score and damage the rest of the liner, creating greater potential problems in the future. You are far better off removing the liner completely to ensure a proper VIP.

The epoxy liners can be a bear to remove and you can plan on a solid week of tumbling to do it, so the shop's estimate in the OP's post is not out of line. There's not much labor involved but it will tie up the tank tumbler for a week.

Steel 72s are cool again as they are popular with side mount divers, and the shop probably knows that. In that regard $120 for a steel 72 that has a fresh hydro, VIP and new valve is not a bad price at all.

 

[Paulmal]

I would have the shop tumble the lining out but if the J valves still work I would use them, they work as well as a K valve and you could use them with a double hose reg if you ever get into antique dive equipment. I have a couple of steel 72's that I J valves on one I had to have sandblasted because the exterior pain could hide rust under scratches. It was epoxy based or automotive paint. Just bought a can of sink galvanizing spray paint from West Marine and painted the tank and have been using it since. The epoxy lining in the old 72's can hide rust as well that is why people have them removed. But it sounds like you will get a good price on the tanks all said and done but not an amazing deal like you thought.

Safe diving.

 

[halocline]

By the time I bought, stripped, painted, and had my 72s inspected (hydro and VIP) I had about $100 each in them and I've never regretted it for a second. They're really fun tanks to dive with. You got a little unlucky with the lining issue. If you do have the LDS do it, make sure they tell you upfront that there will be no charge if they can't get the liner removed entirely. It's not easy on some of them.....and it would be a good idea to ask them if they've removed those liners before, or are they just assuming that the tumbling media they normally use will do the trick.

I agree with the comment about keeping the j valves; they work fine, easy to rebuild, and valves last a loooonnnnnggg time. Just make sure you leave the cam in the down position for diving, otherwise you'll get a little surprise if you breathe the tank down to 3-400 PSI.