quote:

written by Rick da Tech:

Look for an electric water heater. I prefer those with screw in elements (not the ones using four bolts in a flange). When you find one look at the bottom edge. If it's really bad ate up with rust (big holes rusted through the sheet metal), look for another. All will have some rust there. Next open up the lower thermostat cover. If the element and thermostat screws are rusted badly, look for another. This is all assuming you have several to choose from. Elements and thermostats can be replaced at about $10 each.

Pressure test first. The most likely places for leaks are the plumming and fittings attached to the tank. Remove all the plumbing attachments and plug all but two with 3/4" pipe plugs. The remaining fittings (on top) screw in a pipe nipple (about 3" to 4" long) and and ball valves. on one mount a garden hose to pipe adapter on it. Use the other mount a ball valve to bleed the air out. fill the tank with water leaving an air gap at the top. close the vent valve first then let wait till the water stops flowing and close the other one. Wait till morning and open the vent valve slowly. If air rushes out and you don't see a pool of water around the tank, it's probably ok and worth cleaning up. You will probably want to pressure test again later.

Some have made test rigs with schrader valves and pressure guages to perform the tests. I think they can be built for a few dollars with parts from the hardware store.

I don't have links to them but most of the plumbing how to sites give directions for testing the elements to see if it works.