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View Full Version : What to look for when buying used steel tanks



Sasha_K
07-19-2008, 20:41
I'm about to check out one used Steel 72 tank. I know it doesn't have current hydro, but I'm OK with that as the deal is good.

Anything in particular I should look for - i.e. rust or something else?

SlvrDragon50
07-19-2008, 20:42
Ask for all stamped and other markings - picture is best

Splitlip
07-19-2008, 21:00
Steel 72's are cool. I used them for 20 years. But unless you plan on doubling, I think there are better alternatives out there in the way of steel.

But to answer your question, surface rust does not necessarily mean a deal breaker.
What is the service presure of this one?

Sasha_K
07-20-2008, 09:02
I'm buying from non-divers so they don't know :-(. I asked over email if they can copy down the markings and am just hoping for the best.

In terms of alternatives - what do you have in mind. In terms of AL tanks, I'm a bit turned off with the whole negative buoyancy thing. Fair enough, there are AL tanks which are neutrally buoyant, but most of the used AL tanks I saw so far weren't neutrally buouant.

ScubaToys Larry
07-20-2008, 09:43
Just keep in mind... you might be getting into an old steel 72, which is not 72... without their plus rating, they hold just 67 cubic feet. And you may have to have it hydro, tumbled, vis, and a good chance the valve is not too good - many old steels have old J valves, and burst disks that are straight out instead of opposing - so not allowed any more.. so swap that out...

So by the time you're all done - you spend as much or more than buying a new aluminum tank, and just grab a 3 lb weight, toss it on the tank strap - and you're dealing with the same buoyancy and have more air.

cummings66
07-20-2008, 10:33
Yup to what Larry said, some of those old valves had what amounts to a bullet ready to fire at any time in them. Safe? Maybe, but what if it bursts and launches? I think seeing it in person or taking it by a shop for a vis is in order. The vis will reveal what it's going to take if anything to make it ready for usage.

Rileybri
07-20-2008, 11:12
To give you an Idea I just got a ST 72 w/+ rating current viz and hydro (6/08) and new burst disc on a functioning J valve for $40 with air. I would not pay much more than $50 for a working current ST72.

RoyN
07-20-2008, 18:15
Here is a website that should help you choose your tanks.

http://www.huronscuba.com/equipment/scubaCylinderSpecification.html

Make sure look at the weight of the tank as that will effect your buoyancy and trim.

As for a steel 72, I wouldn't get anything less then a steel 80 tank at least imho.

ReefHound
07-20-2008, 18:41
I buy a lot of used stuff and I'm a bit suspicious of people who claim to not know anything about what they are selling. In some cases it may be legit, but sometime I think people just play dumb in order to sell crap.

Sasha_K
07-21-2008, 14:29
I'm definitely re-thinking the decision now guys.

The deal is tempting - $25 only. The guy said he thinks the working pressure is around 2500. He does say it is an older tank, and needs hydro.

Here is the pic - I'm not sure if I can make out the valve out of it - anyone else with better eyes?

http://images.craigslist.org/010206010311010406200807199187cd65e506a3db99000b3e .jpg

CompuDude
07-21-2008, 14:39
I'm definitely re-thinking the decision now guys.

The deal is tempting - $25 only. The guy said he thinks the working pressure is around 2500. He does say it is an older tank, and needs hydro.

Here is the pic - I'm not sure if I can make out the valve out of it

See if you can talk the guy into making the sale contingent on the tank passing inspection, then go for it.

Sasha_K
07-22-2008, 09:11
Question - consider this scenario.

If I get the tank in Seattle, I get it hydroed & visually inspected in Seattle, then I leave the tank open (for shipping to Toronto) , once I get to Toronto do I need to do any inspection again, or can the LDS just screw on the valve for me?

CompuDude
07-22-2008, 14:58
Question - consider this scenario.

If I get the tank in Seattle, I get it hydroed & visually inspected in Seattle, then I leave the tank open (for shipping to Toronto) , once I get to Toronto do I need to do any inspection again, or can the LDS just screw on the valve for me?

Technically it needs to be inspected again. In reality, it's up to your local shop.

cummings66
07-22-2008, 22:52
The cylinder does not need to have the valve removed to ship, nor does it need to lose all it's pressure either. You can ship them with a little pressure in them, not much but I think under 50 psi is fine. Check with the carrier for sure, but I do know I have had them shipped that way to me and it's fine.

MSilvia
07-23-2008, 10:59
once I get to Toronto do I need to do any inspection again, or can the LDS just screw on the valve for me?
If the tank has hydro and vis, what's to stop you from giving the valve threads a wrap with teflon tape and screwing it in yourself? So long as you don't need it to be O2 clean, that is.

cummings66
07-23-2008, 12:23
Well, the issue would be the LDS will probably want to do a vis anyhow.

MSilvia
07-23-2008, 12:32
Well, the issue would be the LDS will probably want to do a vis anyhow.
Based on what? Do they want to vis every tank that comes in with someone else's sticker on it? It's not like you'd have to remove the current vis sticker in order to remove the valve.

If the sticker says it passed vis, why would they want to re-inspect?

CompuDude
07-23-2008, 14:39
once I get to Toronto do I need to do any inspection again, or can the LDS just screw on the valve for me?
If the tank has hydro and vis, what's to stop you from giving the valve threads a wrap with teflon tape and screwing it in yourself? So long as you don't need it to be O2 clean, that is.

Well, first off, you're not supposed to use teflon tape. :smiley21:

Secondly, the issue isn't whether or not they respect the vis sticker from the other company, the issue is any time the valve has come off (within reason) the cylinder should technically be re-inspected. You never know if someone drove the luggage cart under the sprinklers or if it sat in a really high-humidity area for a while with the valve off, or if some small animals or insects crawled in. A re-inspection is also called for (again, technically) if the tank is completely empty, since they never know why.

IMO, empty the tank of all gas, but keep the valve on (and then closed). Assuming it arrives just fine on the other end, take it to the shop and see if they'll fill it. IF they notice the tank is COMPLETELY empty, they may or may not insist on doing a vis, depending on the explanation and how reasonable they are. I think that's the best shot.

MSilvia
07-23-2008, 15:09
Well, first off, you're not supposed to use teflon tape. :smiley21:
Any idea why not? I only suggested it because that's what I've seen done in the past, by more than one shop/instructor.

Secondly, the issue isn't whether or not they respect the vis sticker from the other company, the issue is any time the valve has come off (within reason) the cylinder should technically be re-inspected.For sure, you OUGHT to have it inspected. I was just suggesting you may not NEED to. It's bad advice. Don't take it. My keyboard must have been set to "evil".

IMO, empty the tank of all gas, but keep the valve on (and then closed). I think that's the best shot. Agreed... if you can ship with the valve on, it's best for the tank, and reduces the "risk" of having to go for re-inspection.

CompuDude
07-23-2008, 15:25
Well, first off, you're not supposed to use teflon tape. :smiley21:
Any idea why not? I only suggested it because that's what I've seen done in the past, by more than one shop/instructor.

I don't have my PSI books handy here at work, but I do recall from my training that the only tank valves that are supposed to have teflon tape used are the really old tapered-thread valves. Straight valves should have either nothing, or a tiny amount of Dow-Corning 111 or Christolube (depending on the application) used simply to aid with reduction of a galvanic corrosion.


For sure, you OUGHT to have it inspected. I was just suggesting you may not NEED to. It's bad advice. Don't take it. My keyboard must have been set to "evil".
I agree with you, I was just addressing the technicalities involved. Technically, of course you should. Real world applications often vary. :)

cummings66
07-23-2008, 16:40
Well, the issue would be the LDS will probably want to do a vis anyhow.
Based on what? Do they want to vis every tank that comes in with someone else's sticker on it? It's not like you'd have to remove the current vis sticker in order to remove the valve.

If the sticker says it passed vis, why would they want to re-inspect?

No air pressure would be the basis. I was told by a dive shop they do it because you never know what's in the cylinder, and I had a dive shop show me things in cylinders that come in with 0 pressure. Sometimes owners try to fix things up themselves, the one that comes to mind is somebody who tried to use tape to fix a leaky valve. He had loose tape in the bottom of the cylinder and of course you could tell it was loose the moment you grabbed the valve. It got a vis and failed, the threads in the aluminum were stripped.

crpntr133
07-23-2008, 16:48
Find someone with a transfer whip and put a few psi in it.

BTW, aren't some 72's an odd diameter? Just in case the OP wants to double them up later.