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How to Fix a Water Heater Pilot Light

If your hot water heater suddenly stops working, chances are a bad thermocouple has shut off the gas to the pilot light. Replacement is an easy DIY repair.

By the DIY experts of The Family Handyman Magazine

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    If your hot water heater suddenly stops working, chances are a bad thermocouple has shut off the gas to the pilot light. Replacement is an easy DIY repair.

Replace the thermocouple

No hot water? If you have a natural or propane gas water heater, chances are the pilot has gone out. The pilot is a small flame that ignites the gas burner on your waterheater. When it goes out, first try relighting it, following the directions on the water heater label. If the pilot doesn't relight, or if it goes out right after lighting, by far the most common cause is a bad thermocouple. The good news: You can usually replace a thermocouple for minimal cost and in less than an hour. You'll get your hot water going without waiting for a pro to show up and save the cost of a service call.

To replace the thermocouple, follow the photo series. Be sure to turn off the shutoff valve in the gas line; that is, one quarter turn so that the handle is at a right angle to the pipe. Since working room is tight around the burner, we recommend that you simply unscrew the three nuts at the control valve and pull out the entire burner assembly. You'll see either a slot or clips that hold it in place (Photo 2). Then either unscrew the thermocouple end or pull it out (depending on the water heater) and take it with you to an appliance parts store to find a match. Position it exactly like the old one. When relit, the pilot flame should wrap around the thermocouple bulb.

To reattach the three lines to the gas valve, thread the nuts into place with your fingers and hand-tighten them. Then snug them up with a quarter to half revolution with a wrench. The metals are soft, so don't over tighten.

Be sure to test for gas leaks. You must have the pilot lit and the burner on for this test so that gas is flowing through the large tube. Reopen the shutoff valve, relight the pilot, then turn the control valve to “on”. When the gas burner comes on, use a 50/50 dish soap/water mix to test the screw joints for air bubbles that indicate leaks.

Closed burner chamber

Closed burner chamber

When Not to Replace the Thermocouple

Some gas water heaters have a “closed” burner chamber, which is difficult to access. We recommend that you call a service pro to fix this type. Also, some gas water heaters don't have pilots. Let the pros fix these as well.


You should not be able to smell gas during this operation (except for a slight whiff when you remove the gas lines). If you do, leave the house and call your gas utility.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • 4-in-1 screwdriver
    • Adjustable wrench
    • Wrench set

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

    • Thermocouple
    • Dish soap
    • Long matches(for lighting pilot)

Comments from DIY Community Members

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March 04, 12:06 AM [GMT -5]

I replaced the thermocouple but still have the problem of lighting the wh every day.
After I light the pilot and the main burner fires up, the water heats and later the pilot extinguishes. I did replace the thermocouple but do different ones generate different charges? Is there a special one for a Robert Shaw regulator?

February 13, 10:22 PM [GMT -5]

Thank you for the great tutoring, and I was able to replace the thermo-coupler in my water heater, GE brand Model PG40T9XA. Since the thermo-coupler basically is a solid copper wire, a conductor with thermo sensor at the end. It’s very simple to go to Home Depot and buying an UNIVERSAL THERMO coupler typical one of two sizes 24 inches or 36 inches. For example, My GE water heater has the thermo sensor / copper wire 15 inches long. However, I bought the universal thermo coupler 24 inches long at Home Depot and folding the extra copper wire / thermo sensor .
The point is we don’t have to find / to buy OEM manufacturing part for the exact length of the thermo coupler. An universal thermo couple works just fine.

October 17, 1:47 PM [GMT -5]

Thanks for the help. Now that I have identified the problem I think I might just call heating service in western springs to come help me out. I might just make things worse haha but good advice!

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How to Fix a Water Heater Pilot Light

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