How to Fix An Overheating Water Heater

Control Thermostat

If your hot water appears to be getting too hot, you probably have a defective thermostat. The temperature of your hot water is regulated by this adjustable thermostat which normally has a range between 90 and 150 degrees Fahrenheit. On most residential electric hot water heaters there will be both an upper and lower thermostat and they should be adjusted to the same temperature. To determine which of the thermostats might be defective allow the water heater to sit for about half an hour after running a generous amount of hot water. This will cause the unit to cycle the elements on long enough to stabilize the temperature. Next, turn off the power and then remove the two access covers. Pull the insulation aside and ensure that the thermostats are adjusted to the same settings and are making full contact to the wall of the tank. This is essential for proper temperature regulation. With a small flat blade screwdriver you can adjust the dial to the highest setting and then back to the lowest setting. You should hear an audible click when the thermostat contacts open and close, or you can use a multi-meter to monitor the continuity as you rotate the dial. If a thermostat does not appear to open the contacts when turned to a lower setting, then it should be replaced. Disconnect the wires and lift up on the spring mounting bracket to remove the thermostat. Make sure that when installing the new thermostat the mounting bracket maintains a firm contact between the thermostat and the tank. On gas-fired water heaters the temperature is controlled by the gas valve. The valve assembly will have a dial that will allow for temperature adjustment and will also have a probe that monitors the water temperature. If adjusting the dial does not achieve the desired water temperature, then the valve assembly must be replaced. This repair should only be performed by a trained professional.