Unlike gas water heaters that use gas burners to heat the water, electric water heaters rely on a pair of upper and lower metal heating elements to heat the water. Similar to the way in which oven heating elements work, the heating elements in a water heater heat up when electrical current passes through them. Each of the heating elements is controlled by a separate thermostat.
In an electric water heater, the bottom heating element is the workhorse, since it is at the bottom of the tank where cold water enters from a dip tube that extends down through the tank. The upper heating element really only contributes when there is a high hot water demand and only serves to heat water in the upper portion of the tank. When a hot water tap is opened somewhere in the house, hot water flows up out of the top of the tank, and new cold water flows into the bottom of the tank, where the lower heating element begins to heat it.
Before You Begin
It is usually easy to tell which heating element is faulty. A constant supply of lukewarm water indicates a defective upper heating element, while a short supply of fully hot water indicates a defective lower heating element
Replacing a faulty heating element on a water heater is not particularly difficult, but it is considered an advanced project since it requires both mechanical skill and a comfortable knowledge of electrical wiring issues. It involves three different project stages:
- Testing the heating element
- Removing the old heating element
- Installing a new heating element
Heating elements are not particularly expensive, so you may want to replace both of them, even if only one has tested faulty. If one heating element has gone bad, it is possible the other one will shortly follow, and replacing both can proactively prevent a second repair in the near future. Some manufacturers sell heating elements in repair kits that include both heating elements, as well as the thermostats.
Equipment / Tools
- Non-contact circuit tester
- Garden hose
- Ratchet wrench and sockets
- New heating element (as needed)
How to Test a Heating Element
To test an electric water heater heating element, you will need to be familiar with the use a multimeter.
Turn Off the Power
Turn off power to the electric water heater at the main power panel by turning off the circuit breaker or removing the fuse that controls power to the water heater's circuit.
Wait for the water in the tank to cool—this can take two hours or more. This is very important because the heating elements are controlled by thermostats, and hot water in the tank will affect electrical flow to the heating elements.
Open a hot water faucet and run the water to verify it is cool.
Expose the Heating Element
Remove the access cover panel and the insulation covering the heating element terminal block. Fold the insulation outward and away from the heating element. This will expose the screw terminals where the circuit wires are connected to the heating element.
Use a non-contact circuit tester to test the wires for power. When you have confirmed that the power is off, loosen the screws holding the wires to each of the two terminal screws and disconnect the circuit wires.
Test the Heating Element
To check the heating element, set a multi-tester to the OHMs (continuity) setting, then connect the red lead to one screw terminal and the black lead to the other screw terminal on the heating element.
If the ohm reading is 0 on a digital multi-tester, or if the needle reads infinity (does not move) using an analog dial, there is no flow of electricity through the heating element. This indicates that the heating element is faulty and needs replacement.
If you do get an ohm resistance value using the multi-tester, then the heating element itself is not faulty. The problem may be with the other heating element or in the upper or lower heating element thermostat.
How to Remove a Heating Element
Removal of the heating element can proceed immediately after you have tested the heating element (see above).
Turn Off the Power and Water
If you have not already done so, turn off power to the electric water heater at the main power panel by turning off the circuit breaker or fuse powering the heater (see above).
Turn off the cold water supply delivering water to the water heater. This shut-off valve is usually found just above the water heater, on the cold-water pipe that enters the water heater.
Expose the Heating Element
If you have not already done so, remove the access cover panel and insulation covering the heating element terminal block. Fold the insulation outward and away from the heater element. Test to make sure the power is off, using a non-contact circuit tester.
If necessary, remove the thermostat cover from the thermostat. Make sure to disengage the attachment point linking the thermostat to the heating element.
Loosen the screws holding the wires to each of the two terminal screws and disconnect the circuit wires.
Drain the Water Heater
To drain the water heater, run a garden hose from the drain spigot on the water heater to a floor drain. Open the drain valve and drain water from the water heater tank.
Remove the Heating Element
Remove a screw-in type heating element by turning the element counterclockwise with a ratchet wrench and 1 1/2-inch socket. Some repair kits come with a socket that fits the heating element. Remove the gasket that seals the heating element to the water heater tank.
Remove a flange-type heating element by removing the four screws holding the element in place. Remove the gasket. With the mounting screws and gasket removed, extract the heating element from the water heater tank.
How to Install a New Heating Element
The new heating element can be installed immediately after you've tested and removed the old faulty heating element (see above).
Make sure the replacement element has the correct voltage and wattage rating for your water heater. You can find this information on the flange or terminal block of the heating element or on the water heater’s data plate.
Insert the New Heating Element
Clean the area surrounding where the gasket fastens to the tank, using a rag. Position the new gasket on the heating element and insert the assembly into the water heater tank. Tighten a screw-in type heating element by threading it clockwise into the tank opening with a socket wrench until secure. For flange-type heating elements, insert the four mounting screws and tighten them down securely.
Refill the Water Heater Tank
Close the drain valve on the water heater. Open both the cold water inlet valve and the nearest hot water faucet. Keep the hot water faucet open for three minutes after obtaining a constant flow of water. This will purge the lines of any excess air and sediment.
Check for leaks around the heating element.
Make Wire Connections
Connect the black and white circuit wires by wrapping the wires around the screw terminals on the heating element in a clockwise direction. It makes no difference which wire is attached to which screw terminal. Tighten the screws down completely, then tug on the wires to make sure they are tight.
Reassemble the Cover Plate
Replace the thermostat cover, then tuck the insulation back in place and reattach the heating element cover plate onto the water heater tank.
Turn On Power and Test
Turn on the power by switching on the water heater's circuit breaker. Let the water heat up for several hours, then test the temperature of the water. Make any thermostat adjustments that are necessary.