Buying a used scuba tank doesn’t have to be a daunting experience. There are a lot of places to find them, making a good used tank relatively easy to acquire. Whether you shop online, or from a local seller, a garage sale, or estate sale, there are a few things you want to consider:
Is there any damage to the outside of the tank?
Examine the outside of the tank, top to bottom. Check out the base, and pull off the boot. Look closely at the neck where the valve is inserted. There might be dents in the metal, bubbling paint or discoloration, rust, pitting in the metal, paint chipping, or other signs of water damage underneath the boot and/or at the neck. Anything that could weaken the structural integrity of the metal could prove catastrophic at depth. Steel tanks are more prone to oxidation and degradation than aluminum, but both types should be assessed carefully.
Does the valve O-ring look old?
Take a good look at the O-ring in the valve. You want to check for dings, scrapes, chips, or other defects to the ring. It isn’t a bad idea to change that O-ring out just to be sure. It will only cost you a few pennies. A bad O-ring can blow out at depth and leave you grabbing for your dive buddies air source in a close call.
Does the tank need a visual inspection?
Since Vis’s are due on a yearly basis, it is a pretty good bet your potential tank has an inspection due. If you overlook this assessment you may end with up with a $35.00 surprise on the first fill. Your local dive shop can’t fill that tank until the vis is current. Keep in mind, if you buy a tank with an expired vis, you will be adding cost on the back end of your purchase. Be sure to look for the vis sticker on the tank.
Does the air tank need a hydro inspection?
The Hydro is due every 5 years. Again, your dive shop can’t fill your tank for you unless this pressure tolerance test is current. Look for STAMPED abbreviated dates in the tank, different from the original markings on the tank, a “month/yr”. The most recent year date on the tank should be within 5 years. Buying a tank in need of a hydro means you could be buying a tank with internal cracks or other damage preventing it from containing air/gas at high pressure. Most dive shops will charge nearly $40 to do a hydro. So, if this step is missed you will be paying on the back end of your purchase. And, there is the possibility (in tanks older than 10 years or tanks with visible defects) your tank will fail the Hydro. In Aluminum tanks made before 1990, certain manufactures used a 6351 alloy with an increased propensity for cracking (most commonly Luxfer and Kiddy). An Eddy-Current test ($20-$30) is required on these tanks. Check that stamp!
Does the tank have air in it?
A tank that has been sitting without a full air fill can have moisture damage. Moisture in the tank will cause corrosion and fail your Hydro, or be a safety risk on a dive. Crack the tank to make sure air expels, or put a gauge on it. It might be best to pass by a very old tank with no air and an expired Hydro. Sometimes a really good deal is just too good to be true.
Is the Burst Disk patent?
In the valve, there is a special disk designed to burst with an air pressure over fill. Valves are periodically cleaned, and the burst disk is evaluated for patency. This is usually done at the time of the Vis/Hydro. If the Burst disk has ruptured, indicating an over fill, the valve needs to be examined, cleaned, and the disk should be replaced ($30-$40). This will be in addition to the cost of the Vis/Hydro. Check that stamp date…again!
Scrap metal value of scuba tanks: Lastly, if you failed to do your home-work and have an unusable scuba tank, you can take it to the scrap metal yard and make some money back. Make some calls on scrap metal payment rates first, and get the best price you can.
- Look for external signs of damage. Remove the boot. If it has any dents, deep scratches or rust, then it is unlikely to pass inspection.
- Check the valve for signs of damage (change the O-ring if you buy it), crack it to check for air, and put it on a gauge to check pressure and function.
- Check the inspection dates…then check them again.
- Ask if the tank/valves have been inspected while the seller has had the tank. If these things have been done, the seller is required to retain the receipts from the dive shop or repairing technician. Copies of these records should come with the tank. Ask for them as part of the deal.
If you find defects, if the inspections are lacking, if there are valve issues, or if the paperwork is not available on the tanks, consider passing this deal by! There are lots of other used tanks out there!
Last bit of info – don’t store scuba tanks for long periods on their sides, stacked. Metal is malleable and weight can change the shape over time. Don’t store your tanks on cement or other porous or moisture holding materials – moisture will wick onto the tank metal over time. The safest way to store tanks is upright, against a stable surface (wall), with a chain or some other appropriate retainer. Or store them upright in a metal tank rack.
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Authored by Lisa J Henry
“Be the Sea”