Normally, a water heater is so reliable and maintenance free,
you can practically ignore it. On average, it takes about 13
years for one to go bad, but with faithful maintenance, it can
Rust is the terminal disease for a water heater. Once it eats
through the steel tank and causes it to leak, you have to replace
the unit. Although the tank’s inside surface has a glass coating
baked onto it, this coating eventually cracks and rust begins.
Failure typically begins around the tank-pipe joints, at the
welds or on the bottom where sediment collects.
Heavy sedimentation from the minerals in the water, especially
hard water, causes sediment to pile up on the bottom and trap
heat from a gas burner, raising the temperature on the bottom
higher than normal and stressing the steel tank and glass coating.
On gas units, you can detect this problem by a rumbling or popping
sound that occurs soon after the burner comes on.
The best defense against sediment buildup is to annually drain
the tank through the drain valve and flush it according to the
directions in your owner’s manual. Unfortunately, many manufacturers
use cheap drain valves, so plan to replace it with a more reliable
ball-type valve during the first cleaning.
Besides the glass coating, your water heater’s other defense
against rust is a special rod called a sacrificial anode (see
illustrations) made of magnesium or some times aluminum. The
anode helps stop the chemical reaction that causes the steel
tank to rust. In the process, the anode itself corrodes, or sacrifices,
itself. Anodes typically last five years or longer, and some
heaters have two to prolong the water heater’s life. Replacing
them generally requires a professional.