Scuba Tech Tips – Buying a Used Scuba Tank

Lots and lots of used scuba tanks are really good to use. No problem! Let me explain a little bit.

Alec Peirce with Scuba Tech Tips. Here we have a used cylinder – very used. This particular tank is quite old. This is a steel 72 scuba tank, which was at one time, prior to the aluminum tanks coming out, the standard used in scuba worldwide. Now their pressure rating is 2250; with a full fill they had 65 cubic feet. (I know the numbers don’t make sense but just trust me on that.)

It’s an old steel tank, 40 years old, and it holds 65 cubic feet of air at 2250. It would give you at least an hour underwater. They’re nice tanks: they’re shorter than a standard 80; they’re lighter than aluminum. “What are you talking about? Aluminum is lighter.” The metal is lighter but they’re not at the same size and the walls of the aluminum tank are much thicker. It’s shorter and lighter than the aluminum 80. This is a steel tank wall and you can see it’s quite thin at less than a quarter of an inch. This is an aluminum tank wall and it’s quite thick at more than half an inch. It’s easier to handle and move around: my wife Diana loves these steel tanks and so do I. These were commonly made into double tanks, sometimes triples, and sometimes more.

This is used and you can buy this tank if you would like to. Now how do you know if you should buy it?

First of all, given the choice (unless it’s an awfully good deal), try to buy it through a dive store. If the dive store has been around for more than two or three days, it has a reputation to preserve. They do not want unhappy customers and certainly don’t want them to buy a tank that isn’t good. It’s not good for business. A dive store, generally speaking, will go out of their way to make sure the tank is good. They may even, if you’re fortuned, and it’s a good dive store, give you a short warranty on the tank. “Take this tank and use it for 30 days: go diving, get it filled, and use it a few times. If you’re perfectly happy and the tank works well, we’re happy too. If, within 30 days, you bring it back and say you’re not happy with the tank, we’ll give you back your money.”

That’s why, given the choice, you should buy your used tanks from a dive store. There’s another reason why: if you buy them from a dive store, they will be almost invariably be properly tested. An old tank like this, as an example, has to have a new hydrostatic test on it. This tank has a new stamp on it – it has several stamps, every five years it has been stamped so there’s quite a few on here – but the most current stamp is 10-19: October of 19, which is pretty current.

Editor’s note: This episode of Scuba Tech Tips was originally published December 20, 2019.

It has a current hydrostatic test and a current visual so that means this tank is safe to use. It will need another visual in a year like every other scuba tank; hydrostatic, the structure itself, is good to use for five years. It’s a good tank. How much to pay for it? That’s between you and the store owner. A good steel tank like this sells for between $100 and $150, approximately. Sometimes you can work a deal with the owner and save a bit of money.

This valve is quite modern; the tank will not have a 45-year-old valve on it. Valves that old are simply not good. This has a modern valve and is a real good tank to use. In this particular case, I’d say, sure, save yourselves $150 or more and buy this tank if it will suit your purposes.

Let’s look at this good-looking tank over here. This is aluminum 80, which you are familiar with and have probably been using. This is the type of tank that is most common around the world: Europe, the Caribbean, the South Pacific, and all of North America: the standard aluminum 80-cubic-foot tank at 3000 PSI. This is the tank that we know and love today. As I’ve said, it’s a little bigger and heavier. If you could buy it for $150, it would be a really good deal. These tanks are typically $300, $350, maybe $400 new with a new valve and a boot. But, no, don’t buy this tank. You can’t tell, and it looks better than the aluminum tank, but this tank is not good to buy.

Again, fortunately this was in a dive store. Someone brought it in to have it tested to see if it was good. (They were going to sell it.) A dive store checked it and they found this particular aluminum tank has cracks in the neck. Some of you know this and some of you don’t, but there was an aluminum alloy that was used to make scuba tanks and other high-pressure cylinders as well for many years: from about the mid-70s until maybe 1990. A lot of tanks were made in that timeframe. The alloy they used was discovered to not be good for high pressure cylinders. It suffered from a defect called SLC: sustained load cracking. It means, very simply, that if the tank was full and sat full for any period of time, it could crack. (This is one of those cylinders and we’re going to do a short video on SLC because it’s a bit of a topic that’s almost gone now.)

Although this tank looks really good, put a valve in it and a boot on it, and somebody says, “Hey, give me $200 for this tank.” You just might do that, in which case you’d be buying a dangerous tank and one that wouldn’t be filled. If you took it to any dive store to have a visual and a hydro done, it would fail; and you don’t get your $200 back from an individual. You need to be careful.

Answer to the question “Should I buy a used tank?” Yes. With care. Be sure it has been tested, that your local dive store has looked at it, and has ascertained it is a safe tank that can be filled. You’re all set to go. If it hasn’t been tested, or if you’re getting it off a junk heap, and you have no idea if it’s good or not, be very very careful.

There’s some thoughts for you about buying a used tank. I hope that helps!

Alec Peirce with Tech Tips. Talk to you again soon.