Quote Originally Posted by aris View Post
How often do they fail and for what reasons?

In theory - you could fill it yourself with one of these new inexpensive Chinese 300bar compressors. How wise this is on a bottle out of test is anyones guess.
Not sure of the failure rate but they fail for internal and external corrosion; external can be obvious unless there's a fresh coat of paint on it, internal where sub standard air has been used (not dry breathing air) or a pump without an efficient water filter. Dents, lumps, bumps and gouges, and threads are also examined and the hydrostatic test (immersion in water tank and pressure displacement measured against known figures) carried out. It is assumed an ex-diving tank has more chance of getting water contaminated than a surface fittings tank and this is reflected in the more frequent test period. If the tank fails, you won't (or shouldn't) get it back; the tester is required to cut it up.