Though it is not common, there are times when the water in a water heater becomes too hot. There are three components that could cause this to happen. The temperature relief valve, thermostats and heating elements should all be checked if the water is too hot. The do-it-yourself homeowner can troubleshoot these parts and determine where the problem is.
Temperature Pressure Relief Valve
Hot water heaters are designed with a temperature pressure relief valve. It will relieve pressure and drain water if the water temperature becomes too hot. Testing the temperature pressure relief valve is a quick process. Locate the valve on the side of the water heater. It will have a tub running below it and a flip switch on it. Lift the switch halfway and allow it to snap back down. You should hear a gurgling sound, which means it released some water pressure. If you did not hear anything, the valve should be replaced by a professional.
First check to see what the temperature setting is on the thermostat. When water heaters are installed, they are usually set to 140 degrees Fahrenheit. The optimal temperature setting should be 120 degrees Fahrenheit. Most likely, the water heater will be running and should shut off if you turn the thermostat down. If it doesn't, the thermostat will need to be replaced.
Make sure that the thermostat is flush against the tank. If the thermostat is not flush, it will not get an accurate temperature reading and will keep the water tank heating. Adjust the thermostat flush to the tank by loosening the mounting screws and readjusting it. Be sure to tighten the screws back down after adjustment.
The heating element could be grounding out, which will result in the heating element staying on. When this happens the heating element will burn out prematurely after heating the water to excessive temperatures. To check it, remove one wire from the element terminals and set a volt-ohm meter to RX1. Touch one probe to each of the terminals on the heating element. You should receive a reading of zero. Any other reading and the heating element needs to be replaced.