Originally Posted by SenorWanderer
anyone care to explain what tests are performed when you need it? is it a structural issue, to make sure the cylinder isn't damaged and won't explode? what is it that could happen to a cylinder to cause it to fail?
The test is a hydrostatic test, often refered to as a hydro. For a detailed explanation of the test check this link: http://en.wikipedia.org/wiki/Hydrostatic_test
The most common reason for failure is rusting of the tank. For this reason you don't ever want to let your tank bleed completely out ( i.e. don't open the valve without the regulator attached) and leave the valve open. The humidity in the air can begin the rusting process. The rust will create a weak spot that can eventually fail. The rusting process may take years before it actually gets weak enough to be a problem. Even if you are always careful not to let room air in, you don't know if a previous owner has, especially if you exchange tanks rather than refill. The hydrostat test is cheap insurance against what could be fatal consequences.
Normally I have my tanks refilled. However, when they are with a year of needing recertification, I take them to a place that exchanges tanks. This way I avoid having to pay for testing. It usually costs me $2-3 more to exchange than refill, but that is a big savings in having to pay $20-25 for the test.
Bugeater Brewing Company