Would you consider buying a used tank?

[Boogie711]

to a carbon wrapped tank, for a couple of reasons -

a) if it's too light (bouyant), there's no value, since you need to just add weight to your belt anyway. I'd rather have a heavy tank than a heavy belt.

b) I understand the water can get in between the layers on carbon fibre, causing no end of harm.

 

[1Scubanewbie]

Recently I took 3 tanks I purchased used to Rocky Mountain Fire and Safety. I was quoted $22.50 for a hydro and inspection. I also saw that they pressure tested the tanks (3000 AL) to 5000 psi. I'm a little new to this game. I had someone tell me on another thread that its dangerous to over pressure AL tanks because it will shorten the life of the tank. Additionally this guy tried to charge me $29 when I went to pick them up. Needless to say I'll probably just take them to the Scuba Shop next time because it'll save some hassle factor.

 

[Boogie711]

But - aside from the $$ issue, they did nothing wrong.

To hydro test a tank, you take it up to 5 thirds of it's rated pressure. For a 3000 PSI aluminum tank, you do indeed crank it up to 5000 psi. It's designed to measure the elasticity of the metal.

Actually, this was covered in Class One of my OW Certification - I don't know if that's standard for all agencies, but anyway...

You may not want to do that all the time to an aluminum tank, but hydro testing once every five years is fine. Well - even if it isn't fine, there isn't much you can do about it. It has to go to 5000 psi.

 

[Scuba_Jenny]

HI
I have learned more about tanks in this thread than in my past years of diving. I had a AL80 that was susposed to go into hydro. But the LDS said they couldn't hydro it because it was a KM (I think thats what it was, it was a name). Said that their hydro place refused these tanks and that there was nothing I could do. I switched it out for a used Catalina, keeping the stem I had for $80. I thought I got a good deal since I don't ahve to look for another tank and would never buy new.
Any thoughts?
I do feel I was treated right by the LDS, I have been going there since I was certified and the guy I delt with, I trust.

 

[DA Aquamaster]

I have a total of 15 steel 72's as well as 4 steel Faber 71.2's and I bought them all used. Most of the 72's are seventies vintage but a few are late 60's vintage and two are ICC marked tanks from 1965. All pass hydro with flying colors and barring getting water in the tank and leaving it there, a steel tank will last for at least 50 years. The guy I dive with runs a hydro test facility in addition to a dive shop and he tests steel welding tanks made prior to WWI and they still easily pass hydro. The problem is finding a spot on the shoulder to stamp the new test date.

I find that on average they need tumbled about every 10 years to remove flash rust that eventually adds up to something that needs to be removed. Hydros every five years are $12.50 including the VIP, and a VIP for the other years is $3.95.

Hydro testing itself is fairly cheap, it is the shipping to get the tank to and from the test facility that costs bucks and the tendency for dive shops to repeat the VIP (it's a required part of the hydro test process) and slap their own sticker on the tank that runs up the cost. Some shops just plain gouge divers on the hydro charge as well. I have heard quotes of $40 to $50 per tank and that is basically robbery.

As for original purchase cost, I have probably paid an average of $60 per steel 72 (with current hydro and current VIP) and paid $112.00 each for the late 90's vintage Faber 71.2's. In 18 yrs I have purchased exactly one used tank that failed a VIP and that was from a dive shop that exhanged the bad tank for another.

For the most part steel 72's are under valued and very good buys on the used market. They last forever, have excellent bouyancy characteristics, and as long as your SAC rate is good, will allow you to dive with your buddies with AL80's.

I get a little concerned with some of the larger steel tanks popular with the tech diving set as they are often routinely overfilled. I would make a purchase of a tank from a tech diver contingent on the hydro test and the expansion results.

Buying an aluminum tank is more of a crap shoot as they are more sensitive to fatigue from overfilling (and some dive operators/divers push them as hard as 4000 psi) and also to heat. You also have to consider the alloy used in the tank and the increasing number of fatigue prone AL tanks that are showing up with neck and shoulder cracks.

 

[DA Aquamaster]

scuba_jenny once bubbled...
the LDS said they couldn't hydro it because it was a KM (I think thats what it was, it was a name). Said that their hydro place refused these tanks and that there was nothing I could do.

On occasion a tank will have an exemption rather than a normal certification and if the exemption expires the tank must be removed from service. There are several types of aluminum tanks with exemptions but I have never heard of this with a scuba tank.

Luxfer tanks made from the 1972 through June 1988 as well as all Walter Kidde tanks were made with 6351 T-6 Aluminum and this alloy is implicated in numerous instances of fatique cracks in the neck and shoulder area and there have been a few explosions. An additional eddy current inspection is required with tanks using this alloy, but the tanks are still approved for service. Kidde tanks have heavier walls than Luxfer tanks and expand a bit less during hydro tests. I can't see that a hydro test facility would refuse to test one.

 

[Scuba_Jenny]

The short synopsis had to do with taxes. Apparently there is something out there that was never enforced and now they (whoever they are) are cracking down. Walter Kitty does sound familiar, but I may be wrong.
In the slight chance of a tank explosion or other problems, I would be rather safe than sorry.

 

[DA Aquamaster]

The good news is that Catalina never used 6351 T-6 aluminum in their tanks, so you should not have that worry with your current tank.

 

[pasley]

scuba_jenny once bubbled...
I switched it out for a used Catalina, keeping the stem I had for $80. I thought I got a good deal since I don't ahve to look for another tank and would never buy new.

I bought brand new Catalina AL 80 for $99.00, at Sport Chalet including the new valve which I think is a better deal.

The following tanks are made from the now banned AL alloy and suspect for rapid stress fractures:

All DOT-3AL tanks manufactured under one of the following exemptions or special permits: 6498, 7042, 8107, 8364, 8422
All composite cylinders manufactured under one of the following exemptions: 7235, 8023, 8115
All Walter Kidde DOT-3AL scuba tanks.
All Cliff Impact DOT-3AL scuba tanks made before July 1990.
All Luxfer 80.8 cu. ft. scuba tanks (S80.8) made before May 1987.
All Luxfer 72 and 100 cu. ft. scuba tanks (S72, S100) made before August 1987.
All Luxfer 80 cu. ft. scuba tanks (S80) made before January 1988.
All Luxfer 50 and 92 cu. ft. scuba tanks (S50, S92) made before April 1988.
All Luxfer 30 and 63 cu. ft scuba tanks (S30, S63) made before May 1988.
All Luxfer 40 cu. ft. scuba tanks (S40) made before June 1988.
All other scuba tanks made in the US before February 1990 (except Catalina).
All scuba tanks not made in the US.

Note Catalina never used the AL alloy in question. I know in some places dive shops refuse to deal with any tanks on the above list. Since they are the ones who get injured if it blows during a fill, I can't say I blame them.

 

[PacNWdiver]

Faber/OMS 98

Tank = $120
Vis = myself, free
Hydro (plus rating) = $12

Not too bad when you consider new ones sell on the street for about $280.

John