A cold shower is a shocking way to start the day. Your water heater pilot light does more than just ignite the gas; it acts as a safety gatekeeper. If the pilot light won’t stay lit, the main burner will not ignite, and your water will eventually turn ice cold.
While this can be frustrating, it is often a solvable issue. You might be able to fix it yourself with a few basic tools and a bit of patience. Here is a guide to troubleshooting a pilot light that keeps going out.
Key Takeaways
- Check the thermocouple: This sensor is the most common culprit; look for dirt, bends, or damage.
- Inspect airflow: Strong drafts, dirty vents, or a clogged air intake screen can snuff out the flame.
- Examine gas flow: Kinked flex tubes or a dirty pilot tube can restrict the fuel needed to keep the light burning.
- Know when to call a pro: If the main control valve fails or you smell a gas leak, seek professional help immediately.
9 Reasons Why Your Water Heater Pilot Light Won’t Stay Lit
If you are tired of relighting the flame only to see it go out minutes later, one of these issues is likely to blame.
1. Damaged Thermostat or Gas Valve
The gas valve (often called the gas control valve) acts as the brain of your water heater. It regulates the flow of gas to the pilot and the main burner. If this component fails, it may cut the gas supply completely, killing the pilot light.
A damaged upper thermostat is a likely suspect if your water stays cold despite a lit pilot, while a faulty lower thermostat often causes water to run hot before quickly turning cold.
The Solution
You can test this with a multimeter. Locate the thermostats and check for electrical continuity. If the reset button pops out, press it to see if that resolves the issue.
Sometimes a simple temperature adjustment works. However, if the control valve itself is broken, you cannot repair it. You must replace the unit. This generally costs between $100 and $300, plus labor if you hire a pro.
2. Obstructed Thermocouple
The thermocouple is a safety device that detects heat from the pilot flame. It sends a small electrical signal to the gas valve to keep the gas flowing. If the sensor gets dirty, it cannot sense the heat. The system assumes the flame is out and cuts the gas to prevent a leak.
This is arguably the most common reason a pilot light won’t stay lit. Carbon buildup and dust act as insulators, blocking the heat transfer.
The Solution
Wait for the thermocouple to cool completely. Take a piece of fine-grit sandpaper or emery cloth and gently sand the tip of the sensor to remove soot and grime. Relight the pilot. If it stays lit, you have solved the problem. If not, you may need to replace the thermocouple.
3. Bent Thermocouple
The thermocouple must be positioned precisely within the pilot flame to work. If the sensor is bent or shifted too far away from the flame, it won’t get hot enough to generate the voltage needed to keep the gas valve open.
This often happens during cleaning or if the water heater was bumped.
The Solution
Visually inspect the thermocouple. The tip should be enveloped by the blue part of the pilot flame. If it looks bent away from the flame, wait for it to cool. Gently bend it back into position so the flame touches the top half-inch of the rod.
4. Damaged Thermocouple
Thermocouples degrade over time. If cleaning and repositioning the rod does not work, the internal components may have failed. Even if it looks physically fine, it might not be generating the necessary voltage.
The Solution
You can test the voltage with a multimeter. A healthy thermocouple should generate a reading above 20 millivolts. If the reading is below this threshold, the part is dead. Fortunately, thermocouples are inexpensive and relatively easy to swap out with basic tools.
5. Dirty Pilot Tube
Gas travels through a small pilot tube to feed the flame. Because the orifice at the end is tiny, it can easily clog with dust, dirt, or debris. If the gas flow is restricted, the resulting flame will be weak and yellow rather than strong and blue. A weak flame won’t heat the thermocouple enough to keep the valve open.
The Solution
Turn off the gas and let the unit cool. Disconnect the pilot tube and use a thin needle or compressed air to clear any blockages. Reassemble the tube and attempt to light the pilot.
Top Tip
A healthy pilot flame should be sharp blue. A lazy yellow flame indicates a lack of oxygen or a dirty tube.
6. Defective Flex Tube
The flex tube connects the gas controller to the burner assembly. If this tube gets kinked, twisted, or pinched, it restricts the gas supply. Without a steady stream of fuel, the pilot light will sputter and die.
The Solution
Inspect the supply line for any sharp bends or physical damage. If it looks twisted, try to straighten it out gently to restore flow. If the tube is cracked or severely damaged, replace it immediately to avoid dangerous gas leaks.
7. Faulty Main Control Valve
If you have ruled out the thermocouple and fuel tubes, the problem might lie with the main control valve itself. This component uses a solenoid to hold the gas valve open. If the solenoid fails, the valve will close regardless of the signal from the thermocouple.
The Solution
This is not a DIY repair for most homeowners. The valve needs to be replaced entirely. Given the complexity and the involvement of gas lines, it is best to hire a certified plumber.
8. Strong Drafts or Airflow Issues
While electrical issues are rare in standard atmospheric heaters, airflow issues are rampant. Strong winds can blow down the vent pipe (downdraft) and extinguish the pilot.
Additionally, many modern water heaters have a “flammable vapor sensor” or a screen at the bottom of the unit. If this screen gets clogged with lint and dust, the flame suffocates from a lack of oxygen.
The Solution
Check the area for drafts. Ensure the vent cap on your roof is secure. If you have a sealed combustion unit, vacuum the air intake screen at the base of the water heater. Keeping this screen clean ensures the fire gets the oxygen it needs to breathe.
9. Faulty Burner
A dirty or corroded burner can cause inconsistent ignition. If the burner ports are clogged, the flame may lift off the burner or fail to spread smoothly. This instability can disturb the pilot flame and cause the safety system to trip.
The Solution
Observe the main burner when it ignites. It should light up within 4 seconds with a smooth “whoosh.” If it pops, bangs, or struggles to light, the burner likely needs cleaning or replacement. This job often requires removing the burner assembly, so calling a professional is a safe bet.
Investigation Is Vital
Troubleshooting your water heater helps you determine the problem quickly. Even if you cannot fix it yourself, knowing the symptoms helps you communicate effectively with a plumber.
A pilot light that won’t stay lit is usually a minor component failure rather than a sign that you need a new water heater. Start with the thermocouple, check for drafts, and work your way down the list.
FAQs
How Do I Know If My Thermocouple Is Bad?
The most common sign is that the pilot light ignites while you hold the control knob down but goes out immediately when you release the knob. You can also test it with a multimeter; a reading below 20 millivolts usually indicates a failure.
Is It Safe To Relight a Pilot Light by Myself?
Yes, it is generally safe to relight a pilot light if you follow the manufacturer’s instructions located on the tank. However, if you smell gas before you start, do not attempt to light it. Leave the area and call your gas utility provider immediately.
Why Does My Pilot Light Go Out When It Is Windy?
High winds can create a downdraft that pushes air down your exhaust flue, blowing out the flame. Ensure your vent cap is undamaged and installed correctly. If the problem persists, a professional may need to install a high-wind cap.
