To repair an electric hot water heater, correctly diagnosing the problem is important. In order to make this diagnosis, the person in charge of the repair must know a little about the water heater in question. The person must determine if the water heater was installed correctly and was it working properly before the problem developed? If the answer is yes to these questions, then the repairperson can move on to troubleshooting the problem.
If the problem is water that is not hot, check the thermostat. Two thermostats are located in most electric water heaters. One of these thermostats is located near the top of the tank and the other one near the bottom. Both thermostats have a removable metal cover plate and are pressed firmly against the bare metal wall of the tank.
The thermostat located on the top generally will have a high limit switch that trips if the water overheats and once tripped, the electricity is shut off to both the heating elements. When this upper limit switch has been tripped, it is usually an indication that there is another problem with the water heater. To reset this switch, locate the red button on the thermostat and press it. Now check for power at the input terminals of the upper thermostat.
If it is determined that no power is present, the circuit breakers will need to be checked and the wiring to the water heater. After checking the thermostat, the breaker and the wiring, check the top heating element as the upper thermostat applies power to this heating element. If the heating element has power but is not getting hot, then replace it. If there is no power at the heating element, then replace the upper thermostat.
If the problem is not enough water or the water temperature being too low the reason could be the result of the lower thermostat being defective. The upper thermostat removes power from the upper heating element and transfers it to the lower thermostat and lower heating element. To trace the problem, check for power at the upper thermostat where it sends the power to the lower thermostat and heating element.
If there is no power here, then the upper thermostat is bad and needs replacing. If this upper thermostat has power then check the power at the lower heating element, if there is no power at the lower heating element, then the lower thermostat needs replaced. However, if the lower heating element is getting power, it should heat up. It is does not, then it will need to be replaced. A broken dip tube could also be the problem, so check it and replace if necessary.
If the problem is that the water is too hot, then the culprit is probably one of the thermostats. To solve this, check the power at the top heating element. If there is power here, then the top thermostat is defective. If there is power at the bottom heating element, the bottom thermostat is defective and needs replaced. One other reason for over heating could be that the thermostats are not pushed firmly against the tank.
If the problem is a leaking relief valve, then check for a blockage such as a check valve or pressure-reducing valve that could have a defective bypass. If this occurs, the increased water volume has no place to go and the pressure increases. Another reason a relief valve will fail is if the water temperature gets too high. An expansion tank, placed in the line at the inlet, creates a place for the increased volume to go and will solve most of the problems with a relief valve leaking.
If the problem is a popping or banging noise, built up scale could be on the heating element. This build up can cause all sorts of noises while heating up. To fix this problem, remove the heating elements and either clean them or replace them.
If the problem is odor related, bacteria that can react with the magnesium anode rod are probably causing it. Solving this problem is usually as simple as cleaning the tank with chlorine bleach or changing the anode rod to aluminum.
If a leaking tank were the problem, the only way to solve this would be to replace the tank.