How to Repair a Gas Hot Water Heater Thermocouple

A thermocouple is a safety device on a hot water heater that detects when the pilot light has failed. If the pilot light is out, the thermocouple signals the gas control valve to stop supplying gas. Repairing a thermocouple means replacing the broken or malfunctioning device. It's an easy job, and new thermocouples are inexpensive to purchase.

• 1

  Turn off the gas supply to the hot water heater by shutting off the valve located on the incoming gas line to the hot water heater.

• 2

  Turn the water heater's temperature control to "OFF."

• 3

  Open the access cover to the gas control valve and thermocouple. This cover is usually held in place with a couple of screws.

• 4

  Remove the old thermocouple by loosening the nuts that secure it into the gas control valve. You'll need an open end wrench to loosen the nut that locks the thermocouple in place. The device is a long, narrow tube that runs from the gas control valve to the point where the pilot light flame should be. Take a look at how the old thermocouple is attached at the pilot light. Hot water heater manufacturers employ different methods for attachment, so observing how your heater is set up will help you replace the device.

• 5

  Pull out the old thermocouple and replace it with one that is the same length. Thermocouples are available at most hardware and home centers.

• 6

  Hand-tighten the locking nut that holds the new thermocouple to the gas control valve until it feels snug, then finish tightening with an open end wrench. Hand-tightening helps to prevent cross-threading and stripping out the threads.

• 7

  Re-open the main gas supply valve and relight the pilot light following the manufacturer's instructions, which are written on the water heater. Usually, this entails turning the gas control valve to "PILOT," igniting the pilot light with a lit match or lighter, holding the valve down for several minutes as the thermocouple heats, then turning the valve to "ON."

• 8

  Place the access cover back on and turn the temperature control valve until the burners ignite.