How to Relight a Gas Water Heater Pilot Light

A gas water heater with no hot water is often nothing more than a pilot light that’s gone out — a draft, a dip in gas supply, or a worn thermocouple can all snuff it out. Relighting it is a five-minute job on most tank-style gas water heaters, and this guide walks through it safely from start to finish.

Relight a Gas Water Heater Pilot Light: Quick Overview

Relighting a water heater pilot light means turning the gas control knob to Pilot, holding it in while you light the pilot flame with the igniter or a long lighter, and holding the knob for about a minute so the thermocouple heats up enough to keep the gas valve open on its own. If the pilot won’t stay lit even after a few tries, the thermocouple has likely worn out and needs replacing — a cheap, DIY-friendly part covered below. If your water heater trips a breaker or the issue turns out to be electrical rather than gas-related, see our guide on how to reset a tripped circuit breaker. And if you’re weighing whether an aging water heater is worth repairing at all, our repair or replace decision tool can help.

What’s Actually Wrong

Pilot lights go out for a few common reasons: a draft from a nearby vent or door, a temporary dip in gas pressure, dust or debris clogging the pilot orifice, or a failing thermocouple — the small copper safety sensor that sits in the pilot flame and signals the gas valve that it’s safe to keep supplying gas. If the pilot relights but won’t stay lit for more than a few seconds once you release the knob, a worn thermocouple is almost always the cause, and it’s an inexpensive part that most homeowners can replace themselves in under 30 minutes.

Tools You’ll Need

• Long fireplace lighter or barbecue lighter
• Flashlight
• Adjustable wrench (only if replacing the thermocouple)
• Replacement thermocouple (only if the pilot won’t stay lit)

Step-by-Step: Relighting the Pilot

1. Confirm there’s no gas smell. Follow the safety warning above before doing anything else.
2. Find the gas control valve. It’s on the front of the water heater near the bottom, usually with a dial labeled Off, Pilot, and On.
3. Turn the knob to Off and wait 5 minutes. This clears any residual gas from the burner chamber.
4. Turn the knob to Pilot. Most valves require you to push the knob in slightly to allow gas to flow to the pilot.
5. Light the pilot. While holding the knob in, use the igniter button if your unit has one, or insert a long lighter through the access port to ignite the pilot flame. Continue holding the knob in for about 60 seconds.
6. Release the knob slowly and check the flame. The pilot should stay lit on its own. If it goes out when you release the knob, repeat the process once more, holding slightly longer.
7. Turn the knob to On. Once the pilot stays lit consistently, turn the main control to the On position and replace the outer access panel.
8. If it still won’t stay lit, the thermocouple likely needs replacing: turn off the gas supply, unscrew the old thermocouple from the gas valve and pilot bracket, install the new one finger-tight plus a quarter turn with a wrench, and repeat the lighting steps above.

Watch the Repair

This is gas, so it is worth watching before you touch anything. Rheem’s own instructions show the wait, the control-knob positions and the igniter sequence on a modern sealed-combustion heater.

When to Call a Pro

Call a licensed plumber or your gas utility if you ever smell gas, if the pilot won’t stay lit even after replacing the thermocouple, if you see soot or a yellow (rather than blue) pilot flame, or if the water heater is more than 10-12 years old and showing other signs of failure like rust-colored water or popping noises — at that point a full replacement is often the more sensible move.