A pilot light that won’t stay lit is a symptom of a failing thermocouple. Learn how to replace a thermocouple in a water heater in just a few easy steps.
Turn off the gas and remove the old thermocouple. Install a new one and test for gas leaks. Replace the doors and you’re all done.
How to Replace a Thermocouple in a Water Heater
A failing water heater thermocouple prevents the pilot light from remaining lit. The thermocouple is a safety device that detects whether or not the pilot light is lit.
If it is not lit, the gas supplying the pilot is turned off and the gas valve will not switch the main burner on.
When a thermocouple begins to wear out, it cannot correctly detect if the pilot is lit or not. Follow these easy steps on how to replace a thermocouple in a water heater.
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Turn Off the Gas
Turn off the gas valve that supplies the water heater. Usually, it is located on a pipe just before it enters the water heater gas control valve. Most manufacturers also recommend turning off the gas control valve.
Push it in, and hold it in while turning it to the off position. Don’t leave this step out; gas water heaters can be dangerous if you do – gas could escape while you changing the water heater and it only takes a spark to cause a fire or explosion.
Remove the Old Thermocouple
Remove the outer and inner doors to the gas burner. The thin copper tube leading from the gas control valve is the thermocouple. Follow this to where it is attached to the pilot light assembly by a bracket.
Some brackets are held in place by a screw, others clip into place. Remove the thermocouple bracket from the pilot light bracket assembly.
Remove the thermocouple from the gas valve with a small adjustable wrench. Most can be turned using a 7/16-inch wrench as well. Thermocouples are reversely threaded; turn it clockwise to loosen the nut.
Be careful not to bend any part of the thin copper tube that leads from the gas control valve to the thermocouple – you can use it as a sort of template to bend the new one if it comes coiled up.
Install the New Thermocouple
Bend the new thermocouple tube to the same shape as the old one. Install the new thermocouple into the gas control valve and tighten it firmly, but do not over-tighten it, or it will be damaged.
Remember the threads are reversed; turn it counterclockwise to tighten. Place the thermocouple on the pilot light bracket assembly, and install the screw or clip, that holds it in place.
Finishing Up: Replace the Thermocouple Water Heater
Turn on the gas valve that supplies the water heater. Test the thermocouple connection to the gas control valve with soapy water. No bubbles mean no gas leak.
Follow the manufacturers’ instructions to light the pilot. Check the pilot light to make sure the flame heats the last 1/2-inch of the thermocouple.
Turn the water heater control valve to ON and the main burner should light. Replace the inner and outer doors and you’re all done with how to replace a thermocouple in a water heater.
