Why does my water heater pilot light keep going out?

The most common cause is a worn thermocouple or thermopile, the sensor that sits in the pilot flame and tells the gas valve it is safe to stay open. When it weakens, the valve shuts the gas off a few seconds after you release the knob. Other causes are a dirty or partly clogged pilot tube, a draft blowing the flame out, a failing gas valve, or on newer heaters a tripped flammable-vapor sensor.

How do I relight a water heater pilot light?

Turn the gas control knob to Off, wait five minutes for any gas to clear, then turn it to Pilot, press and hold the knob or the pilot button, and click the igniter until the pilot lights. Keep holding for 30 to 60 seconds, release, and turn the knob to On. If the pilot goes out when you release the knob, hold it longer once; if it goes out again, stop and call a plumber.

Can I replace a thermocouple myself?

It is a common repair, but it involves the gas control and burner assembly, and on many newer heaters the sensor is a sealed part of the burner unit. If you are not comfortable working on gas, or the heater is in an attic, call a licensed plumber. Hugo Plumbing comes out for free and quotes the repair before starting.

What if I smell gas near the water heater?

Do not try to relight anything. Leave the house without touching switches, call the gas utility or 911 from outside, and wait for them to check. A faint gas smell right at the pilot for a second after a failed lighting attempt is normal; a persistent smell in the closet or attic is not.

Water Heater Pilot Light Won’t Stay Lit? Causes, the Safe Way to Relight It, and When to Stop Trying

If the pilot lights but goes out when you release the knob, hold the knob down a full 60 seconds and try once more; if it goes out again, the thermocouple is worn and needs replacing. If the pilot will not light at all, the pilot tube is clogged, the flammable-vapor sensor has tripped, or the gas valve has failed. And if you smell gas: stop, leave, call the utility.

First, the Gas Rule

A faint whiff at the pilot for a second after a failed attempt is normal. A gas smell in the closet, garage, or attic that does not clear is not. Leave without touching light switches, call the gas utility or 911 from outside, and read what to do if you smell gas. Everything below assumes you do not smell gas.

How to Relight It Safely

Turn the gas control knob to Off. Wait five minutes so any gas in the burner chamber clears.
Turn the knob to Pilot.
Press and hold the knob (or the separate pilot button) and click the igniter button, or hold a long lighter to the pilot on older units. Watch through the sight glass for the flame.
Once lit, keep holding for 30 to 60 seconds. This gives the thermocouple time to heat up and signal the gas valve.
Release. If the pilot stays lit, turn the knob to On. The main burner should light within a minute.

What Each Symptom Means

Lights, then dies when you let go. The thermocouple (or thermopile, on units with an electronic gas valve) is not producing enough voltage to hold the valve open. Sometimes it is just dirty or bent out of the flame; usually it is worn. Replacement is the standard fix.

Lights, then dies minutes or hours later. A draft from a nearby vent, an attic fan, or a door blowing the pilot out; a partly clogged pilot tube producing a weak, lazy yellow flame that does not heat the sensor; or a gas valve that is starting to fail.

Will not light at all. Air in the line after a gas outage (keep trying in 30-second cycles); a clogged pilot orifice; no spark from the igniter; or on heaters made after 2003, a tripped flammable-vapor (FVIR) sensor, which locks the unit out after it detects vapors or after the air intake screen clogs with lint and dust. Some units reset after cooling; many need a plumber to reset or replace the sensor and clean the screen.

Main burner lights but the pilot goes out afterward. Often a venting or combustion-air problem, especially in a tight closet. This one deserves a professional look because it can involve carbon monoxide.

Houston Specifics

Attic heaters collect dust and insulation fibers on the air-intake screen and pilot assembly, which is the most common reason we find for a lazy pilot or a tripped FVIR sensor here. Garage heaters near a dryer or a car pick up lint and fumes. Cleaning the screen and pilot tube fixes a surprising share of “pilot won’t stay lit” calls, and it is part of our water heater maintenance service.

When to Stop and Call

Stop if the pilot fails on the second careful attempt, if you smell gas, if the flame is yellow and weak rather than blue and steady, if the unit is more than 10 years old, or if it is in the attic and you would rather not work on gas up there. A thermocouple or gas valve repair is usually quick and inexpensive; on a tank past 10 years we will tell you honestly whether it is worth doing, since a failing gas valve on an old tank is often the start of the end. Our no hot water guide covers the electric side and the other causes, and the water heater repair page covers the service.

Hugo Plumbing comes out for free, 24/7, and quotes the repair in writing before touching anything. Our $30 repair coupon applies.

If your pilot won’t stay lit, call Hugo.