Troubleshoot and Repair an Electric Water Heater

Electric Water Heater Basics
Electric water heaters look similar to their gas-fueled cousins. They both use an insulated storage tank jacket made of steel with insulation between the storage tank and the tank jacket to reduce heat loss of the heated water.

The main difference between electric and gas water heaters is the heat source. In an electric water heater, the water is heated by electric upper and lower heating elements that extend into the water tank. Gas water heaters have a gas burner that heats the water from below the tank.

Problems with little or no heat usually are caused by a failed heating element, an inexpensive part that is relatively easy to replace. Other problems may be due to improper settings, high home water pressure, or a lack of tank maintenance.

Warning: Turn off the Power
Electric water heaters are high-voltage (240-volt) appliances that are dangerous to work with when the power is on. Before checking any electrical parts of a water heater, shut off the power to the heater’s circuit by turning off the appropriate breaker in your home’s service panel (breaker box).

Also, test all wires in the water heater with a non-contact voltage tester to confirm the power is off before touching the wires.

The Problem: No Hot Water
A water heater that produces no hot water may not be getting power, or it may have a tripped limit switch or one or more failed heating elements. First, check the water heater’s circuit breaker in the service panel to make sure it hasn’t tripped. If it has, switch it off, then switch it back on again.

If the heater’s breaker did not trip (it is still on), try to reset the high-temperature limit on the heater:

  • Turn off the breaker to the water heater’s circuit in the service panel.
  • Remove the access panel for the upper heating element on the water heater.
  • Remove the insulation and the plastic safety guard, being careful not to touch any wires or electrical terminals.
  • Press the red button—the high-temperature cutoff reset button—located above the upper thermostat.
  • Replace the safety guard, insulation, and access panel.
  • Turn on the heater’s circuit breaker.
  • If that doesn’t solve the problem, test each heating element and replace it, if necessary.
  • The Problem: Inadequate Hot Water
  • If your water heater is producing hot water, but not enough of it, your unit could be too small to meet the household’s hot water demands. Make sure the demand does not exceed the capacity of the water heater. The water heater should have 75 percent of its capacity as hot water. For example, a 40-gallon water heater is properly sized for a demand of 30 gallons. If the demand is too great for the heater capacity, try to limit the length of showers (and/or install a low-flow showerhead) and spread out dish-washing and laundry to different times of the day.

If your unit is not undersized, or it suddenly produces less hot water than it used to, one or both of its heating elements may have failed. A constant supply of lukewarm water during a shower is indicative of a defective upper heating element. Hot water that runs out quickly during a shower is indicative of a defective lower heating element.

  • The Problem: Water Temperature Too Hot
  • Too much hot water can be almost as frustrating as not enough hot water. If you’re experiencing this problem, it’s possible that one or both of your water heater’s thermostats is set too high.

To check the thermostat settings:

  • Turn off the power to the water heater in the service panel.
  • Remove the access panel, insulation, and plastic safety guard from each heating element on the water heater. Do not touch any wires or electrical terminals.
  • Test the wires to confirm the power is off, using a non-contact voltage tester.
  • Check the heat setting on both thermostats: they should be at the same temperature. The recommended setting is between 115 and 125 F.
  • Adjust the temperature to the desired setting, using a flathead screwdriver.
  • Adjust the other thermostat to the same setting.
  • Replace the safety guard, insulation, and access panel for each element.
  • Turn on the heater’s circuit breaker.