At some point in the home you might find yourself in a situation where you faced with the task of diagnosing and repairing a leaking water heater. The probability of you being able to do the repairs by yourself or even at all is dependent on where the leak is located on the unit.
Generally speaking, a water heater is consists mainly of the following: a water tank, burner assembly and control for the burner, a pressure relief valve, a thermostat and a drain. The fuel used is usually oil, natural gas or electricity but irrespective of the fuel that is used, they all function in the same way.
The very first thing you should do is inspect the unit to find where the leak is located. In order to do this, turn off the power (whatever it might be) supply to the burner and lock the water inlet valves to the tank. In a situation where the leak appears to be coming out of the overflow, this is an indication that the pressure relief valve is leaking and need to be fixed. Place a bucket underneath the overflow outlet and then open the relief valve by pulling the lever that is attached to it. Allow the valve to flush out very well to ensure that there is no mineral buildup or any debris stuck in the valve assembly. After it has been flushed out properly, if the valve is still leaking, then it needs to be replaced altogether.
If the leakage is from one of the inlet or outlet pipes then you will have to figure out which pipe it is and determine if the leakage is coming from either a joint between two pipes or from a fitting connecting the pipe to the heater itself. If it is the case of just a loose fitting, all you have to do is to tighten this but in the event that a pipe is broken or cracked, you might have to employ a plumber's services.
If the leak is located underneath the tank then you will be required to take a look at the drain fitting. The options are to tighten it, close the valve tighter or replace the valve altogether. In order to install a replacement, you need to drain the tank after closing the water inlet valves and draining out the tank. Most often the drain valve is the same specification as the standard water valve that is fitted around your home and you can simply attach a hose to it and run the drain water outside.
Once the tank is totally drained, you may now replace the drain valve. The other possibility that you could be faced with is that the tank may be rusted out at the bottom near the burner. You can take off the burner cover plate and have a look under the tank with the aid of a flashlight to check if there is rust or a puddle of water at the area. If this turns out to be the case then the water heater will have to be replaced.
Once you have successfully located and repaired the leak, you may turn back on the water supply to the tank. After it has filled up, relight the burner.