Electric water heaters have a number of sensors that help determine when the tank needs more water, when the water needs more heat, and when the water has become hot enough. The unit has two thermostats to aid this process: one in the upper part of the water heater, which is where warm water rises towards, and then a lower thermostat near the bottom of the water heater.

Problems with the lower thermostat can cause malfunctions in the electric water heater's heating process. Your unit can then fail to heat water thoroughly, which leaves you with lukewarm water when you want to take a hot shower.

If you own a multi-meter and know how to use it, you can conduct the basic functionality test on the lower thermostat but should still call a plumber to replace the broken part. Don't have experience? Leave the testing and the replacement to a plumbing and heating company, like Able Plumbing-Pumps & Well Service.

What You Need:

  • Owner's manual
  • Insulated screwdriver
  • Clean, empty bucket
  • Multi-meter with ohms setting

Step 1: Access the Lower Thermostat

Turn off the electricity to the unit at the circuit box before performing any tests.

Look around the bottom exterior of your water heater to find the access panel or use your owner's manual for guidance. Use a screwdriver to remove the screws holding the panel door into place. Place the screws and panel door in a clean bucket for safekeeping and so your screws don't roll away on you.

Lift a corner of the insulation material covering the thermostat and gently peel it back, making sure not to tear the material. Remove the cover from the thermostat and place it in the bucket.

You should now see the rear of a thermostat, which includes two terminals with wires attached.

Step 2: Test the Thermostat

Carefully remove the wires from the terminals. If you're using a multi-meter instead of an ohmmeter, make sure the readings are set to ohms before you begin. Attach the probes of the ohmmeter or multi-meter to the two terminals.

Now place the end of your insulated screwdriver into the screw-like device near the terminals, which is called a set screw. Turn the set screw in a clockwise direction while looking at your ohmmeter readings. If no readings show up, your thermostat needs replaced.

If you do get a reading, the thermostat has continuity so there might be another problem at hand. Call in a plumber for further diagnosis and repairs.

Step 3: Reassemble the Water Heater

If the thermostat gave a reading, you can put your unit back together until a plumber can come and check the rest of the unit.

Remove the probes from the terminals and the screwdriver from the set screw. Replace the wires onto the appropriate probes. Retrieve the thermostat cover from the bucket and return it to the back of the thermostat. Push the insulation material back into place and then retrieves the panel door and screws from the bucket.

Screw the panel door back into place. Restore electric to the unit.