Replacing a Thermostat on Water Heater Systems

What You'll Need
Masking or duct tape
Replacement thermostat

Replacing a thermostat on your hot water system can be necessary when it fails to heat water to the right temperature. If you have tried other troubleshooting recommendations to no avail, you may try replacing the old thermostat. Replacing a thermostat produces the best response when you change it for an exact, or very similar, make and model. Look on the back of the thermostat to find the number you will need for the replacement.

Step 1 - Remove the Old Thermostat

Before you go any further, ensure that you have turned off the electricity at the mains supply, which will be either in your garage or close to the front door. You can take a piece of duct tape, or any tape really, and place this over the switch so that it cannot be turned back on accidentally.

Now remove the covers from your thermostat by unscrewing the panels. Thermostats are located at the top and bottom of the water heaters, so work out which one needs replacing. Once inside the panels, unscrew the thermostat from the mounting plate and remove it. You may need to take out any wires which connect the thermostat to the heater.

Step 2 - Install the New Thermostat

Place the wires into the new thermostat. You should be able to see where each wire goes, but follow the instructions on the manufacturer's manual in order to be absolutely sure. When you finish the wiring, screw the thermostat into the mounting panel and push both of these back into position. You can use the screwdriver to turn the thermostat's dial to around 120 degrees. Do not make it any higher than 140, however, as this can cause burns.

Step 3 - Test If Replacing a Thermostat Has Worked

Once you have plugged in the new thermostat, go downstairs and turn on the power. You will need to do this before you seal the panel, in order to check that replacing a thermostat has solved your problem.

You should wait around an hour for the power to come back into the heater. Once the power is restored, start running a hot tap. Leave that running while you check the controls on the new thermostat, to ensure that it is warming correctly.

Step 4 - Finish the Installation

When you are satisfied that the water is heating sufficiently, turn off the power again and screw the thermostat tightly into place. Return the access panels and start the power back up. Your new thermostat is now ready for regular use.