Water Heater Pilot Light Keeps Going Out? Causes and What to Do

A water heater pilot light that keeps going out usually means the thermocouple (the safety sensor that holds the gas valve open) is worn or out of position, or that drafts, a venting problem or a dirty pilot are starving or blowing out the flame. Here’s how to tell the causes apart in a San Jose home.

Less often the gas supply or the gas control valve is at fault. If you smell gas, stop: leave the house and call 911 and PG&E from outside. Otherwise, one relight by the instructions on the heater’s label is reasonable, and a pilot that goes out again needs a licensed plumber.

First: Do You Smell Gas?

If you smell gas near the water heater or anywhere in the house, PG&E’s instructions are:

• Leave the area now and take everyone with you.
• Call 911, then PG&E at 1-800-743-5000, from a safe distance.
• Don’t create a spark. No light switches, phones, flashlights, matches or vehicles until you’re well away.
• Don’t look for the leak with a flame, and don’t relight the pilot.

Don’t go back in until PG&E or the fire department says it’s safe. If the gas was shut off at the meter, PG&E asks you not to turn it back on yourself: PG&E or a qualified professional does a safety check, restores the gas and relights the pilots.

Why Does a Pilot Light Keep Going Out? (October 2026)

Is It the Thermocouple or Flame Sensor?

On a standing-pilot water heater, a thermocouple (or on some models a thermopile) sits in the pilot flame. While it’s hot, it powers a safety valve inside the gas control that keeps gas flowing to the pilot. A.O. Smith explains that if the thermocouple is broken, the pilot won’t stay lit once you release the pilot knob. The same thing happens when the tip is dirty, bent or has slipped out of the flame, or when its connection at the gas valve is loose.

This is the most common reason a pilot lights fine and then goes out, and it’s a routine repair. Newer heaters with electronic ignition have no standing pilot: they use an igniter and a flame sensor, and when the sensor can’t prove there’s a flame, the control shuts the gas off and shows a status code.

Drafts and Venting Problems

A.O. Smith names drafts as a common reason a pilot won’t stay lit: a door left open, a window, a fan, or wind coming down a damaged flue. Moving the draft source away is often enough.

Venting problems are more serious. The flue has to carry combustion gases out of the house; if it’s blocked, disconnected or rusted through, or the heater can’t get enough combustion air, the flame can falter, and PG&E lists “water heaters with improper venting” among common sources of carbon monoxide. A.O. Smith warns that poor airflow can release unburned fuel or carbon monoxide and says to have a technician fix it before you relight. Signs include soot or scorch marks around the burner door, a disconnected vent pipe, or a carbon monoxide alarm. Stop using the heater and call.

A Dirty Pilot or Blocked Air Intake

A healthy pilot flame is steady and mostly blue and wraps around the thermocouple tip. Dust, lint or a partly clogged pilot tube can leave it small, yellow or flickering, too weak to keep the thermocouple hot. A.O. Smith also points to kinked or clogged gas tubes and to blocked air screens that restrict combustion air.

Water heaters in garages and laundry areas collect lint and dust at the base. Keep the area around the heater clear and swept, and never store gasoline, paint or solvents near it. Cleaning the pilot assembly or the air intake is a job for a plumber.

Gas Supply Problems

The pilot can also go out because it isn’t getting enough gas. Check that the shutoff valve on the gas line to the heater is fully open. If your range or furnace is acting up too, or there’s been recent work on the gas line or meter, the problem may be outside the heater. A.O. Smith notes that recurring gas pressure problems usually come from outside the water heater. Problems at the meter or in PG&E’s service are PG&E’s to fix; problems in your house piping are a plumber’s. If an earthquake gas shutoff valve has closed, have it reset and the pilots relit by PG&E or a qualified professional.

A Failing Gas Control Valve

The gas control valve (the box with the knob) holds the pilot safety valve. If a new thermocouple doesn’t fix the outages, the valve may be at fault, and A.O. Smith says it will most likely need to be replaced. That’s licensed gas work.

How Should You Relight the Pilot?

Follow the lighting instructions on the label on your water heater; they differ from model to model, and the label and owner’s manual take precedence over any general guide. In general terms:

• Don’t relight if you smell gas. Leave and call instead.
• Turn the gas control off and wait before relighting so any gas can clear. PG&E says five minutes; A.O. Smith says at least 10 minutes for its heaters. Use the longer time on your label.
• Use the heater’s built-in igniter if it has one, and hold the control as the label says.
• If it won’t light, or goes out again soon after, stop. PG&E says to call PG&E or another qualified professional if you can’t relight the pilot yourself.

On electronic-ignition models, there’s no pilot to light: follow the restart steps in the manual, and if the status light shows a fault, call for service.

Never Bypass a Safety Device

The thermocouple, the safety shutoffs built into modern tanks and the gas control’s safety valve exist to stop gas from flowing when there’s no flame. Never prop or tape the pilot knob down, jumper a thermocouple or thermal switch, or reset a tripped safety shutoff without finding out why it tripped. A heater that keeps shutting itself off is telling you something is wrong; a plumber should check it before it runs again.

What Can You Safely Check Yourself?

• Sniff for gas before anything else. If you smell it, leave and call.
• Make sure the gas valve on the line to the heater is fully open.
• Look for drafts: open doors or windows, fans, a missing burner access cover.
• Clear stored items, lint and dust from around the base, and keep flammable liquids away.
• Look (without touching) at the vent pipe above the heater: is it connected and intact? Any soot or scorch marks?
• Check that your carbon monoxide alarm works. PG&E recommends a UL-approved alarm as a backup to good maintenance, and the CPSC recommends CO alarms with battery power or a battery backup on every level of the home and outside sleeping areas.
• Relight once by the label’s instructions, if there’s no gas smell.

Anything beyond that, such as removing the burner cover, cleaning the pilot or replacing a thermocouple, involves the gas controls and the burner, and belongs with a licensed plumber.

When Should You Stop and Call a Licensed Plumber?

• You smell gas (call 911 and PG&E first, from outside).
• The pilot goes out a second time, or won’t stay lit when you release the knob.
• You see soot, scorch marks, a flame rolling out of the burner area, or a disconnected or damaged vent.
• A carbon monoxide alarm sounds, or anyone has headaches, dizziness or nausea near the heater. PG&E’s advice: turn the appliance off if it’s safe to, get everyone out, call 911 if anyone has symptoms, and don’t use the appliance again until a qualified professional says it’s safe.
• The burner or pilot shut down through a safety switch, or the status light shows a fault.
• The heater is old, leaking or rusty, which may make replacement the better call.

Rheem lists a pilot light that won’t stay lit among its signs to call a plumber, for natural gas and propane heaters alike.

Repair or Replace?

A thermocouple, a pilot cleaning or a venting repair is usually worth doing on a heater in good condition. A failed gas control valve on an older heater, or a pilot problem on a tank that also leaks or rusts, is a good time to price a replacement. Most tank water heaters last about 8 to 12 years.

In San Jose, a new gas water heater typically costs $1,500 to $4,500 or more installed, with the permit and code items. Under the Bay Area Air District’s adopted Rule 9-6, typical home gas water heaters manufactured after January 1, 2027 must be zero-NOx; a Board vote on November 4, 2026 may move that date to 2028. A working gas heater can stay, but if yours is near the end of its life, price a heat pump water heater too. See Bay Area zero-NOx rules and our signs your water heater needs repair.

Pilot Light Problems in San Jose: What’s Different Here

• PG&E supplies the gas across San Jose and the South Bay, so a gas smell or a meter problem goes to PG&E first.
• Garages and laundry rooms are where most South Bay water heaters sit, and lint, dust and stored items there are common reasons for a weak flame.
• Earthquake valves: a closed seismic shutoff valve cuts gas to every pilot in the house; it needs a leak check before it’s reset.
• Permits: if the fix turns into a replacement, the City of San José requires a permit and inspection, which we handle.

Related reading: no hot water? what to check first, causes of water heater failure and water heater maintenance tips.

Get Your Pilot Light Problem Fixed

CPI Service repairs gas water heaters throughout San Jose and the South Bay: thermocouples and flame sensors, pilot assemblies, gas control valves, igniters and venting, with a carbon monoxide check before we leave. Every repair is quoted as a fixed price before we start, and our work carries a 1-year labor warranty. We’re licensed under CSLB License #1101278 (C-36 Plumbing), BBB A+ Accredited, offer same-day service and answer a 24/7 emergency line.

See gas water heater repair and installation or all water heater services, request a free estimate or call (408) 978-3093. Replacing the heater? Ask about $250 off water heater installation.

Sources

• PG&E: Gas Safety
• PG&E: Dangers of Carbon Monoxide
• CPSC: Carbon Monoxide Information Center
• PG&E: Understanding Gas Outages
• A.O. Smith: How To Relight A Water Heater’s Pilot Light
• A.O. Smith: Is Your Hot Water Not Getting Hot? Common Causes and What to Do
• Rheem: 7 Signs You Need to Call a Plumber

Checked October 2026.