Who used up all the hot water?! This Fix-It Guide on electric water heater repair tells how an electric water heater works, what often goes wrong, how to identify an electric water heater problem, and what parts and tools you will need to fix it. It gives instructions for how to troubleshoot an electric water heater thermostat, how to test and replace a heating element, how to test and replace a high-limit cutoff, how to drain an electric water heater tank, how to test and replace a relief valve, and how to replace an electric water heater drain valve. It also refers to heating element repair and electric service panel repair.
How Does an Electric Water Heater Work?
Components of a typical electric water heater.
A water heater is an apparatus for heating water and then storing it for later use. A residential water heater typically warms water to a temperature between 120° and 140°F. When a hot-water faucet is opened, hot water flows from the top of the tank toward the faucet, and cold water enters the tank to replace it. In an electric water heater, the thermostat senses a drop in the water’s temperature and completes an electrical circuit to the heating elements. Electric water heaters usually have both an upper and a lower heating element; each is controlled by a separate thermostat. Once water in the tank reaches the set temperature, the thermostats stop the flow of electricity to the heating elements. In addition, an anode (magnesium) rod attracts impurities in the water that would otherwise attack the metal tank.
Fix-It Tip
Many homes are located in areas with hard water. The contaminants in the water supply build up over time, creating a layer of sediment on the bottom of the water tank, hindering the heater’s performance and shortening its life. You can slow this process by softening the hard water and by lowering the temperature to 130°F or less. Also, to minimize sediment, purge your tank every few months. Simply drain off 2 or 3 gallons of water from the tank, then let it refill.
What Can Go Wrong with an Electric Water Heater?
Because electric water heaters are simple in operation, few things can go wrong with them, and solutions are relatively easy to figure out. Heating elements and thermostats fail. The high-temperature cutoff may trip. The pressure relief valve may malfunction. Sediment can settle in the tank.
How Can I Identify an Electric Water Heater Problem?
- If there is no hot water, first push the reset button on the high-temperature cutoff; test the thermostats and replace if faulty (see below). Test the heating element(s) and replace if faulty (see below).
- If there is not enough hot water, adjust the thermostat settings. As needed, reset, test and replace thermostats and heating elements if faulty.
- If the water is too hot, adjust the thermostat settings and reset. Test and replace the thermostat or high-limit cutoff (see below).
Fix-It Tip
How hot is “too hot” for your water heater? Homes with standard dishwashers typically require a setting of about 120°F, though energy-efficient models preheat incoming water. Homes with an energy-efficient model or without a dishwasher are typically set for about 110°F.
- If the heater leaks, check the pressure relief valve and if the leak persists, replace the valve (see below). Tighten mounting bolts on the heating element gasket and replace if needed.
- If the tank is rusted, replace the water heater.
- If the electric water heater is noisy, drain and flush the tank (see below). Replace damaged or scale-encrusted elements.
- If the hot water is dirty, drain and flush the tank. If the drain valve leaks, tighten or replace it (see below). Note: Regularly draining the tank will prolong the life of your electric water heater.
- If your home has hard water, check the anode rod yearly (see below) and replace it if necessary.
What Do I Need for Electric Water Heater Repair?
Replacement parts are available from local hardware and plumbing supply stores. The tools you will need to fix an electric water heater include these:
- Wrenches
- Screwdrivers
- Multimeter
- Hose
- Pipe tape
- Knife
What Are the Steps to Electric Water Heater Repair?
Caution!
An electric water heater is a 240-volt appliance that can deliver a fatal shock. Always turn off power to the heater at the electrical service panel before beginning work, and verify that power has been shut off. Make sure others in the house know not to restore electricity prematurely. If you have any doubt as to whether electricity has been turned off, seek professional assistance.
Troubleshoot an electric water heater thermostat:
- Shut off power to the heater at the electrical service panel and post a sign warning others not to turn it on.
- Unscrew and remove the electric water heater access panel.
- Using a small screwdriver, turn the thermostat dial counterclockwise to lower the temperature, or clockwise to raise it. If the water heater doesn’t maintain the proper temperature, test the thermostat.
- Disconnect one wire to the upper thermostat to test it. Set a multimeter to RX1 (resistance times 1) and touch a probe to the thermostat terminals as indicated in the owner’s manual. Depending on the model and the terminals tested, the tester should show 1 or infinity (open) or about 0 (closed).
- Test the lower thermostat in the same manner.
- If necessary, replace the thermostat. Unscrew it from its mounting and install one of the same model, size, and rating. Once you install it, adjust the thermostat following instructions in your owner’s manual.
Test and replace an electric water heater heating element:
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Turn off power at the electrical service panel and post a sign warning others not to turn it on.
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Remove the access panel on the electric water heater.
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Disconnect one of the element wires and set a multimeter to RX1000 (resistance times 1,000). Touch one probe to an element mounting bolt and the other to each element terminal screw, in turn. If the tester displays anything but infinity ( open circuit), replace the element.
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If necessary, set the multimeter to RX1 and touch the probes to the terminal screws. If there is any resistance reading at all ( closed circuit), then the element is good. If not, replace it. Both upper and lower elements are tested in the same manner.
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To remove the element, first drain the heater.
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Disconnect the remaining element wire. Remove the mounting bolts holding the element in place. Remove the element.
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Replace the heating element with one of the same model, shape, and rating. Make sure you also replace any installation gaskets.
Test and replace an electric water heater high-limit cutoff:
- Disconnect power to the heater at the electrical service panel and post a sign warning others not to turn it on.
- Remove the upper access panel and push the reset button.
- Replace the access panel and turn the power back on. If the water is hot, the reset was the problem. If not, you’ll need to turn the power off again and reopen the access panel.
- Use a multimeter to test the cutoff terminals for continuity. If faulty, replace with an exact replacement part.
Drain an electric water heater tank:
- Shut off power at the electrical service panel and post a sign warning others not to turn it on.
- Close the cold-water supply valve and open a hot-water faucet somewhere in the house (to speed draining).
- Attach a garden hose to the drain valve and run it outside the house.
- Open the drain valve and allow all water to drain out.
- To refill the tank, close the drain valve tightly and open the cold-water supply valve. Also open a nearby hot-water faucet. When a steady stream of water flows from that faucet, the tank is full and the faucet can be closed.
- Once the tank is full, turn the electrical power back on.
Test and replace an electric water heater relief valve:
- Lift the spring lever on the valve to fill a small cup. Check the cup for sediment.
- If no water spurts out, or if water continues to drip after the valve is released, replace the valve.
- Cut power at the electrical service panel and post a sign warning others not to turn it on. Close the cold-water supply valve.
- Drain a few gallons of water from the tank.
- Unscrew and remove the discharge pipe if used.
- Loosen the relief valve with a pipe wrench, then remove the valve by hand.
- Apply pipe tape to the threads of the replacement valve and screw it into the tank by hand. Tighten it with a pipe wrench. Screw the discharge pipe (if any) into the valve outlet.
- Refill the water heater and restore electrical power.
Replace an electric water heater drain valve:
- Shut off power at the electrical service panel and post a sign warning others not to turn it on.
- Close the cold-water supply valve and drain the water heater completely (see above).
- Unscrew the drain valve with a pipe wrench.
- Replace the drain valve with an identical unit wrapping the end with pipe tape.
- Refill the tank and restore electricity.
Fix-It Tip
Need to get replacement parts? Remember to take the old water-heater parts, the heater brand, and the model number with you when you buy replacements. It may save you a trip.
