How to Replace a Water Heater Thermostat

January 24, 2023

If you’ve flushed the water heater tank, determined the unit is receiving power, and followed other troubleshooting steps and its troubles aren’t resolved, it may need a new thermostat. A faulty thermostat can cause your system to run inefficiently. Or, your water heater may not work at all. Here’s a look at how to replace the water heater thermostat to get it working again.

Do You Need a Water Heater Thermostat?

Installing a new thermostat requires some wiring work, so it’s important to be prepared. If you have a gas water heater, the entire gas valve assembly (which includes the thermostat and heat limiting device) will need to be replaced. This can be quite tricky and rather dangerous so you may want to hire a professional. 

Electric water heaters have two thermostats—one for each heating element. If the water is warming up but is not hot enough, the upper thermostat and heating element will need to be replaced. When the water starts hot and then gets cold, you’ll need a new lower thermostat and element.

Turn Off the Power

Switch the water heater off and disconnect the power by shutting off the circuit breaker. The unit should be connected to a 30-amp breaker. Then remove the screws for the access panel on the water heater and remove the panel. Take out the plastic safety panel as well. Using a voltage tester, determine whether electricity is still flowing to the unit. 

Remove the Old Thermostat

Label all the wires connected to the thermostat before you remove them (and create a diagram just to be safe). Now you can disconnect each wire from the old unit. Locate the bracket that holds the thermostat in place against the tank and pry out one side of this bracket. At the same time, twist that side upward so the bracket won’t lock again while twisting the bracket on the other side. If the thermostat is held in place by a mounting clip, remove it and lift out the component.

Purchase the New Thermostat

Thermostats are often interchangeable. Nonetheless, it’s best to replace the old thermostat with the same type and model. Take the part with you when shopping. A store representative can help you match the right component. You can also purchase a replacement bracket if the old one was damaged when you removed it.

Install the New Thermostat

Attach the mounting clip to the new thermostat or slide the thermostat evenly down into the holding bracket. Make sure it locks in place. Reconnect the wiring in the same configuration as before and reinstall the safety cover and access panel. Now you can turn the power back on, but let the water heater run for at least an hour before running the hot water tap.

Can I Replace a Gas Control Valve?

Gas water heaters, as we touched on earlier, are set up a little differently. The assembly that includes the thermostat is located near the bottom on the outside of the water heater. It contains controls for both the temperature and pilot light. The entire component will need to be replaced if the thermostat fails, but this requires working with gas lines and connectors, raising the risk of a gas leak.

Request Help to Replace a Water Heater Thermostat

If you’re not experienced at fixing water heaters, a plumber can more quickly and effectively do the work. They can replace the heating element and perform other repairs if necessary. Service Champions provides water heater services in Northern California. Our technicians are trained to help with any type of repair and can replace the water heater thermostat for you. They’ll also inspect the unit to ensure it’s safe, reliable, and efficient. To get started, schedule your visit online or call 833-600-0991.

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