Quick Answer: A water heater pilot light that keeps going out is most commonly caused by a failing thermocouple, a dirty or clogged pilot tube, or a draft near the unit that blows out the flame. The thermocouple is a safety sensor that detects the pilot flame and allows the gas valve to stay open. When it fails, the gas valve shuts off and the pilot goes out. This is the most common repair for gas water heaters and can be resolved with a water heater service call. If you smell gas at any point, leave the house and call your gas company immediately.
Relighting the pilot light on your water heater once is a minor inconvenience. Relighting it every few days or every week is a clear sign something needs fixing. Here is how to diagnose and address the most common causes, and when to leave it to a professional.
The Thermocouple: The #1 Cause
The thermocouple is a small metal probe that sits in the pilot flame. It generates a tiny electrical signal that tells the gas valve the pilot is lit. When the thermocouple detects a flame, the gas valve stays open and allows gas to flow to the burner when the thermostat calls for heat. When the thermocouple does not detect a flame (because it has gone out or the thermocouple has failed), the gas valve closes as a safety measure.
A thermocouple fails for three main reasons. It has simply worn out over time (they are designed to last 5 to 10 years). It has become coated with soot, carbon, or mineral deposits that insulate it from the flame. Or it has shifted position so the pilot flame is no longer making proper contact with the sensor tip.
If the pilot lights and stays lit for a few seconds but then goes out as soon as you release the control button, the thermocouple is almost certainly the issue. It is generating enough signal while you manually hold the gas valve open, but not enough to keep the valve open on its own.
A thermocouple is an inexpensive part (typically $10 to $25), but replacing it involves working with gas connections. If you are not experienced with gas appliance repair, have a licensed plumber handle it during a water heater service call. An improperly seated thermocouple can create a false sense of security while allowing a potentially dangerous condition.
Dirty or Clogged Pilot Tube
The pilot tube is the small gas line that delivers gas specifically to the pilot light. Over time, dust, debris, or spider webs can partially block the tube, reducing the gas flow to the pilot. A weak pilot flame may not reach the thermocouple properly, triggering the safety shut-off.
Cleaning the pilot tube requires shutting off the gas, removing the burner assembly cover, and carefully clearing the tube opening with a thin needle or compressed air. This is a more involved repair that most homeowners should leave to a professional who can also inspect the burner assembly and the full gas connection while the unit is open.
Drafts and Ventilation Issues
Gas water heaters need adequate air supply for combustion, but they are also vulnerable to drafts that can blow out the pilot flame. A water heater in a garage with a door that opens frequently, near a window, or in a utility area with cross-ventilation can experience repeated pilot outages simply from air movement.
Check whether the pilot goes out more frequently when garage doors are opened, when nearby windows are open, or on windy days. If so, the solution may be as simple as installing a draft shield around the pilot area or relocating the unit away from the draft source.
Also check the exhaust vent (the metal flue pipe running from the top of the water heater up through the roof). A damaged, disconnected, or obstructed vent can cause downdrafts that push air back down through the flue and extinguish the pilot. A blocked vent is also a carbon monoxide hazard and should be corrected immediately.
We have covered how cold weather affects water heaters, and temperature-related draft changes are one factor that causes seasonal pilot outages.
A Failing Gas Valve
If the thermocouple has been replaced, the pilot tube is clean, and there are no drafts, the gas control valve itself may be failing. The gas valve is the large dial-operated unit on the front of the water heater that controls both the pilot and the main burner. Internal components can degrade over time, preventing the valve from staying open even with a good thermocouple signal.
Gas valve replacement is a professional-only repair. It involves disconnecting the gas line, removing the existing valve, installing the replacement, and testing the entire system for leaks. This is not a DIY project.
Safety First: When to Stop Trying to Relight
If you smell gas when you approach the water heater (a strong rotten-egg odor), do not attempt to light the pilot. Leave the area immediately, do not operate any electrical switches, and call Southern California Gas Company at 1-800-427-2200 from outside the house.
If the pilot has gone out and you see soot or scorching around the burner area, if the flame is yellow or orange instead of blue, or if the unit makes unusual noises during ignition, stop using it and call a plumber. These are signs of combustion problems that go beyond a simple thermocouple issue.
We have addressed gas line safety comprehensively in our gas line repair guide for Los Angeles, including what qualifies as a gas emergency and the proper response steps.
How Long Should a Pilot Light Last?
A properly functioning pilot light should stay lit indefinitely. If yours is going out more than once a year, something needs to be repaired. The longer you continue relighting a failing pilot, the more you risk a situation where gas accumulates before ignition, creating a small flash or puff-back that can cause burns or damage.
If your water heater is over 10 years old and the pilot keeps going out alongside other signs the unit needs professional attention, the cost of repairing an aging unit may not be justified compared to a water heater replacement. Your plumber can advise based on the overall condition of the unit.
Contact Papa’s Plumbing for water heater pilot light diagnosis and repair. We serve homeowners across the Los Angeles area, including Lake Balboa, Tujunga, North Glendale, and La Canada Flintridge.
Frequently Asked Questions
Can I relight the pilot light myself? Yes, if you follow the manufacturer’s instructions on the label of the gas control valve. Turn the dial to “pilot,” press and hold the igniter button (or use a long match for older units), and hold the control button for 30 to 60 seconds after the pilot lights. Release the button slowly. If the pilot stays lit, turn the dial to your desired temperature. If the pilot goes out when you release the button, the thermocouple needs replacing.
Is it dangerous if the pilot light goes out? Modern gas water heaters have safety valves that shut off gas flow when the pilot goes out. The unit will not release gas into the room. However, if you smell gas despite the pilot being out, the safety valve may have failed and you need to evacuate and call SoCalGas immediately.
How much does it cost to replace a thermocouple? A thermocouple replacement by a licensed plumber typically costs $100 to $250 including the part and labor. It is one of the least expensive water heater repairs and is usually completed in under an hour.
Should I switch to an electric water heater to avoid pilot light issues? Electric water heaters eliminate pilot light and gas combustion concerns entirely, but they cost more to operate in areas where electricity rates are higher than gas rates. For most LA homeowners, maintaining a gas water heater properly is more cost-effective. If you are considering a change, our tankless vs traditional comparison covers the pros and cons of different fuel types and heating methods.
