How to Fix a Water Heater Pilot Light


It’s Monday morning and just as you’re about to rinse out the shampoo from your hair and Icy cold water starts cascading down your body. It’s happened to all of us and it can easily ruin your day – but don’t worry, replacing the thermocouple usually does the trick.

If your hot water has suddenly stopped working, there’s a good chance that a bad thermocouple has shut off the gas to the pilot light and lucky for you, replacement is an easy DIY repair.

What is a Thermocouple?

A thermocouple senses the heat of the pilot and allows gas to flow to the burner. A bad thermocouple will shut off gas to both the pilot and the burner, so the pilot won’t stay lit.

If you have a natural propane gas water heater and you suddenly don’t have hot water, chances are the pilot has gone out. The water heater pilot is a small flame that ignites the gas burner on your water heater. When the pilot goes out, try relighting it by following the directions on the water heater label. If the pilot doesn’t relight, goes out right after lighting or if the pilot light keeps going out, the most common cause is a bad thermocouple. There’s good news though! You can usually replace a thermocouple inexpensively in less than an hour and you’ll get your hot water going without waiting for a pro to show up and you’ll save the cost of a service call for a repair. Keep reading to learn how to light a pilot light.

To replace the thermocouple, follow the photo series. Make sure you turn off the shutoff valve in the gas line; one quarter turn so that the handle is at a right angle to the pipe. The working room can be tight around the burner so we recommend that you simply unscrew the three nuts at the control valve and pull out the burner assembly completely. You’ll see either a slot or clips that hold it in place (Photo 2). Then you can 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! Make sure you put it in exactly like the old one and when relit, the water heater pilot flame should wrap around the thermocouple bulb.

When reattaching the three lines to the gas valve, use your fingers to thread the nuts into place and hand tighten them. Use a wrench to tighten them ever so slightly with a quarter to half revolution. Don’t overtighten them as the metals are soft.

Make sure you test for gas leaks. The pilot must be lit and the burner on for this test to be sure that gas is flowing through the large tube. Reopen the shutoff valve, relight the pilot and then turn the control valve so that it’s on. When the gas burner comes on, use a 50/50 mixture of dish soap and water to test the screw joints for air bubbles as this indicates leaks.


The only time you should be able to smell gas during this operation is the slight whiff when you remove the gas lines. If you smell gas other than that make sure you leave the house and call your gas utility.

You Should Not Replace the Thermocouple if…

If your gas water heater has a “closed” burner chamber we recommend that you call a professional to fix this type as it is difficult to access. Some gas water heaters don’t have pilots and if that’s the case for yours, we advise you to let the pros fix these as well!