There is no tried and true way to know precisely when a water heater needs replacement. Obviously, a leak in the body of the heater requires immediate replacement. If there is a major malfunction, such as complete or partial loss of hot water supply, leakage around plumbing fittings, or the appearance of excessive corrosion on the heater body itself or at the heater’s plumbing connections, AND the unit is more than eight years old, replacement may be preferable to repair (if a repair is possible, that is). I would leave this up to your budget and repair skills.

All the active parts and most of the plumbing parts–the heating elements, thermostat, anode rod, and the various valves–are designed to be replaceable. The main obstacle to disassembly is corrosion. A water heater corrodes more quickly than other plumbing fixtures because of the constant high temperature at which it operates, and the fact that sometimes the water heater acts as an electric ground, accelerating this corrosive process. Corrosion makes replacing any parts chancy, since the replacement may leak, necessitating the replacement of the entire heater. So, like a conscientious Boy Scout, be prepared for the possibility of replacement even when the repair seems simple and straightforward. So it goes with plumbing!

In most case’s, with a water heater more than 13 years old, repairs are probably not cost-effective, since the life expectancy of a water heater is only 8-12 years. As they age, they become less efficient. This is true for all heaters, but more for electric types. Modern water heaters have better insulation and are more efficient “out of the box,” so you may notice dramatic savings in fuel and/or electric costs by replacing it.Oh and by the way,check out the Garden section on this site.