If the gas pilot light on a hot water heater refuses to stay lit, replacing its thermocouple may be the answer to the problem.


Step 1: Read the instruction manual or the instructions printed on the hot water heater to familiarize yourself with the manufacture’s recommended method for replacing the thermocouple.


Step 2: Use the gas control knob on your hot water heater to turn the gas off and use the gas shut off valve on the heater supply line to also turn the gas off. If the tank is warm, let it cool for at least 20 minutes.


Step 3: Remove both the outer and inner access panels on the hot water tank.


Step 4: Locate the copper thermocouple line and use an adjustable wrench to loosen the nut that attaches the thermocouple to the gas control box. Once the nut is loose, pull down on the thermocouple to disconnect it from the tank.


Step 5: Follow the copper line to the burner assembly and detach the thermocouple from its bracket. If there is a second nut at the end of the thermocouple, loosen it before wiggling the thermocouple tip out of its mounting bracket. If the burner assembly needs to be removed to access the far end of the thermocouple it may be wise to call in a professional service person.


Step 6: Once the thermocouple is removed, take it to the local hardware store or plumbing supply shop and find a suitable replacement. Universal thermocouples come with multiple tips, so one of these should work. The new thermocouple should be the same length as the old one. If the new thermocouple is longer, loop the excess tubing to make the new thermocouple essentially the same length as the old one.


Step 7: Begin by installing the tip of the new thermocouple back into the bracket on the burner assembly. If there was a secondary nut, tighten it with an adjustable wrench.


Step 8: Push the end of the thermocouple into the gas valve and hand tighten the nut to attach it. Do not cross thread the nut. Use an adjustable wrench to finish tightening the nut. The nut is tight enough when there is little play or wiggle to the copper tubing running into it.


Step 9: Once the thermocouple is securely in place, turn the gas back on and light the burner pilot light. Be sure to follow the manufacturer’s instructions for relighting the pilot light.


Step 10: Replace the inner and outer access panels, put away your tools and give the tank a little time before taking that long hot shower you have been dreaming of.

Thermocoupleare temperature sensors that serve as safety shut off devices for gas appliances.

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