How To Replace The Lower Thermostat In A Water Heater

13 April 2016
 Categories: , Blog


Has your water heater stopped providing consistent heated water? The problem could lie in your lower thermostat. The unit has an upper and lower thermostat that act as sensors for when each segment of the tank's water have reached the desired temperature. A problem with one of the thermostats can leave one half of the heater less warm than desired.

You can test both thermometers for functionality using a multi-meter. If you find that the lower thermostat is bad, you can replace the part on your own with a little bit of effort.

What You Need:

  • Owner's manual
  • Screwdriver
  • Electrical tape
  • Digital camera (optional)
  • New lower thermostat

Step 1: Gaining Access to the Lower Thermostat

Shut off the power to the water heater at the circuit breaker, fuse box, or by unplugging the unit from the wall.

Locate the water heater's access panel, which leads to the thermostat. Consult your owner's manual for help locating the panel, if needed.  Use a screwdriver to remove the screws holding the panel door in place. Pull the door off and set it aside on a table and place the screws on the interior of the door so they don't roll away.

Return to the access hole and pull up the flap of insulation in the opening. Use electrical tape to attach the flap to the exterior wall of the water heater to give you some working space. You will now see a plastic thermostat cover. Pry up the corner with your screwdriver and pull off the cover. Discard the cover.

Step 2: Unhook and Remove Lower Thermostat

Note the orientation of the wires attached to the thermostat's terminals. Take a picture of the setup if you're worried about forgetting. Loosen the screw beside each terminal to free the wires. Pull the wires out of the thermostat and leave the wires dangling in place.

Find the metal bracket tabs on each side of the thermostat. Press the tabs forward to unlock the thermostat. Pull the thermostat up and out to clear the brackets. Discard the old thermostat.

Step 3: Install New Thermostat and Test Water Heater

Insert the new thermostat behind the brackets using the tabs as a guiding track. Press the tabs backward to lock the thermostat body in place.

Hook the wires back up to the correct terminals using your picture if you took one. Tighten the screw beside each terminal to secure. Set the thermostat dial to the suggested temperature for your unit, which can be found in your owner's manual.

Take the new cover out of the packaging and snap it into place over the thermostat. Gently pull the electrical tape off the water heater wall and the insulation. Press the insulation down over the thermostat cover. Put the access panel door back on and secure into place using its screws.

Restore power to the unit at the breaker, fuse box, or plug. Let the water heater run for a while and test the functionality. If you still don't have proper heated water, call in a water heater plumber for help.

For more information, contact Maryland Sewer & Plumbing Service or a similar company.