Long-time divers frequently end up with old SCUBA cylinders that can no longer be used for various reasons. Perhaps diving is a long-forgotten hobby or the tanks may have failed inspection. Often, these tanks end up gathering dust in a garage because there are no clear instructions on how to dispose of them.
Most local dive shops offer annual visual inspections to their customers. These inspections, called Visual Inspection Program (VIP) ensure that each SCUBA cylinder is in proper condition to be filled. During a VIP, a qualified technician checks for rust inside the tank or for the telltale signs of a crack that's beginning to form.
Tanks that show evidence of internal rust are sent out to be "tumbled." The tank is filled about halfway with a cleaning solution and tumbling media. Tumbling media consists of small, rough particles that slough rust off of the inside of the tank. Most tanks can be salvaged through this process, unless the damage has become too severe.
Hydrostatic testing is a more complex test that must be performed every five years on SCUBA cylinders. During the test, the tank is filled with water and submerged in a pressurized, water-filled chamber. That way, if the tank ruptures, it will be less dangerous because it is filled with water instead of highly compressed gas.
A tank that fails this inspection rarely can be salvaged. Once it has ruptured, the tank is no longer useful. At this point, it's time to find a place to scrap the tank.
Local Dive Shop Disposal
When a tank fails hydrostatic inspection, or when visual inspection reveals damage too significant to be affected by tumbling, local dive shops often take charge of the cylinder's disposal.
Failed tanks are marked with an "x" to indicate that they are condemned. Valves are removed for resale, as these are often in fine shape. The cylinders themselves are then sold to scrap metal dealers.
Scrap Metal Dealers
You can bypass your local dive shop and go straight to the scrap metal dealer. It's important that they are empty and the valves removed so that it's obvious the cylinders pose no danger. Scrap metal dealers typically pay by the pound. A garage full of unwanted or unusable tanks could be turned into cash swiftly.
Tanks simply can be delivered to the dump or recycling center. Some individuals at these drop-off locations refuse to accept cylinders, however, in the mistaken belief that they are hazardous. These items, when empty, are benign; it's the intense pressure of the compressed gas that makes the tank volatile, so an empty tank poses no more risk than any other metal waste.
Creatives can try repurposing an old SCUBA tank for new use. Wiring a cylinder for a light bulb can create an interesting conversation-piece lamp. A cylinder that's been cut in half might make an excellent planter. The possibilities are endless if you're willing to get your hands dirty and have a little fun.