Even with proper maintenance, scuba tanks eventually wear out. Dents, cracks, and rust can compromise a scuba tank's structural integrity. The dive industry recommends that tanks be visually inspected for damage once a year, and the United States Department of Transportation requires that all compressed gas cylinders undergo hydrostatic testing every 5 years. If a tank fails either visual inspection or hydrostatic testing, it is decommissioned. The owner is left with a heavy, bulky hunk of metal. Now what?
1. Be Certain That the Tank Is Unusable
If uncertain, double check to make sure that the tank can't be used for diving. Old tanks are not necessarily unusable. If the tank's hydrostatic test date is passed, send the tank in for testing. Steel tanks have a very long life and steel tanks from the 1950's can still be found in perfect working condition.
2. Save the Valuable Bits
Remove the tank's valve. Tank valves are valuable, and a valve in good condition can be re-used or sold. Even if the valve is no longer usable, you will need to remove it before scrapping or shipping the tank.
3. Make Some Cash
Sell the tank for scrap metal.
4. Find an Appropriate Disposal Method
Give the tank to your local dive shop if they already have a method of disposing of old scuba tanks.
5. Get Creative
Use the tank for an art project. From door stops to lamp bases, used scuba tanks can be painted, cut up, and polished for a variety of uses. Scuba tanks even make great planters for the diving gardener.
6. Help to Educate Future Divers
Donate the tank as a teaching aid. Have the scuba tank cut in half and give it to an instructor to use when teaching open water courses. Many students find it interesting to see the inside of the tank and the thickness of the walls. Tanks with rust or significant pitting may be even better teaching aids because they illustrate the consequences of poor tank maintenance.
7. Make more dive gear.
Creative divers have used decommissioned scuba tanks to make camera housings and light canisters.
8. Sell the tank on E-Bay.
If your tank can be fixed but you don't want to bother, put it on E-bay and someone will buy it. Even if it is unfixable, there is surely someone out there interested in buying a decommissioned tank for an art project or teaching aid.
Here are some more ideas from About.com readers:
"One of the Mikes" writes:
My dad has cut a few tanks in half and made wind chimes and a gong. We have one in the front yard, one at the dive shop and my buddy Scott has one over the bar in his Pub. Also, I saw somewhere (I think Sunset House in Grand Cayman) that placed old tanks into the concrete dock and had pipe welded to the side to make them into boat tie-off cleats. We have some at the LDS that are placed in front of the parking spots as stops.
Javier Salas suggests:
Cut it in half lenghtwise, then draw your design using a drill and a combination of different size drill bits and put a light bulb behind it… awesome custom lamp project.