Troubleshooting why water heater pilot light won’t stay lit

Having trouble with your water heater pilot light not staying lit? This guide provides troubleshooting tips to help you identify and resolve common issues that can cause the pilot light to go out.

A water heater’s pilot light is a crucial component responsible for igniting the gas burner and heating the water. However, there are instances when the pilot light won’t light, leaving you without hot water. In this comprehensive guide, we will explore the common reasons behind a non-functioning pilot light and provide detailed fixes to help you get it up and running again. By understanding these issues and implementing the appropriate solutions, you can ensure the uninterrupted operation of your gas water heater.

Importance of a Properly Functioning Pilot Light:


The pilot light in a gas water heater is responsible for igniting the main burner, which provides the heat to warm the water. A properly functioning pilot light ensures the reliable and efficient operation of the water heater. It is crucial to address any issues with the pilot light promptly to avoid inconvenience and potential damage to the unit.

Common Issues with Gas Water Heater Pilot Lights:

Let’s explore some of the common problems that can occur with gas water heater pilot lights:

  1. Pilot Light Won’t Stay Lit: If the pilot light goes out immediately after igniting or won’t stay lit, it could be due to a faulty thermocouple, a malfunctioning gas control valve, or inadequate gas supply.
  2. Weak or Flickering Pilot Flame: A weak or flickering pilot flame may indicate a dirty or damaged pilot assembly, a blocked orifice, or insufficient gas flow. This can lead to inconsistent heating or frequent pilot light outages.
  3. Pilot Light Keeps Going Out: If the pilot light repeatedly goes out after being relit, there may be issues with the thermopile, gas pressure, ventilation, or a draft in the area where the water heater is installed.
  4. Pilot Light Won’t Ignite: When the pilot light won’t ignite at all, potential causes include a depleted gas supply, a malfunctioning ignition system, or an improperly positioned pilot assembly.

Troubleshooting the Reasons Why Your Water Heater Pilot Won’t light

Safety First: Before attempting any troubleshooting, ensure your safety by turning off the gas supply to the water heater. Locate the gas shut-off valve connected to the unit and turn it to the “off” position. This step is crucial to prevent gas leaks and potential hazards during the troubleshooting process.

Problem 1: Igniter doesn’t spark


Begin by visually inspecting the igniter assembly. Look for any signs of damage, such as broken wires, loose connections, or visible wear and tear. Check for any debris or dirt that may be affecting the igniter’s performance. If you notice any issues, such as frayed wires or loose connections, it’s important to address them before proceeding.

igniter of gas water heater

Over time, the igniter can accumulate dirt, soot, or residue, hindering its ability to generate a spark. Gently clean the igniter using a soft brush or cloth to remove any debris or buildup. Avoid using abrasive materials or excessive force, as this could damage the igniter.

The gap between the igniter and the pilot light can affect the spark’s effectiveness. Ensure that the igniter is properly aligned with the pilot light and the gap is set to the manufacturer’s recommended specifications. Use a small tool, such as a screwdriver, to adjust the gap if necessary. Refer to the water heater’s manual or manufacturer’s instructions for specific gap requirements.

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Problem 2: Gas supply Issues

If your water heater pilot light won’t stay lit, one of the first things to check is the gas supply. Insufficient or interrupted gas supply can prevent the pilot light from staying lit. Here are some steps to troubleshoot and address potential gas supply issues:

  1. Check Gas Valve: Ensure that the gas valve supplying the water heater is fully open. Sometimes, the valve may accidentally get partially closed, restricting the gas flow. Verify that the valve is in the “on” position by aligning it with the direction of the gas pipe.
  2. Gas Pressure: Insufficient gas pressure can prevent the pilot light from staying lit. Contact your gas utility provider to check the gas pressure at your home. They can measure the pressure and determine if it falls within the acceptable range for operating your water heater. If the pressure is low, the utility provider will need to make the necessary adjustments.

The inlet gas pressure to a propane water heater should be between 10-13” water column.

The inlet gas pressure to a natural gas water heater should be between 5-8” water column.

Check the gas pressure while the system is off as well as while it is on to make sure that there isn’t too significant of a pressure drop. Measure the pressure at the drip T cap or via the pressure tap on the gas valve. After checking, make sure that no leaks are present.

Problem 3: Clogged Pilot Orifice

The pilot orifice is a small opening where the gas is released to ignite the pilot light. Over time, it can become clogged with dirt, debris, or mineral deposits, obstructing the flow of gas and preventing the pilot light from igniting.

pilot of gas water heater

A clogged pilot orifice can prevent the flow of gas to the pilot light. Carefully remove the pilot assembly and clean the orifice using compressed air or a thin wire. Ensure the orifice is clear before reassembling the pilot assembly.

Problem 4: Thermocouple Problems

thermocouple of gas water heater

If you’re facing difficulties with your water heater’s pilot light not staying lit, one common culprit could be a faulty or malfunctioning thermocouple. The thermocouple is a safety device that senses the presence of the pilot flame and allows the gas valve to remain open. If the thermocouple is not working correctly, it can shut off the gas supply and cause the pilot light to go out. Here are some steps to troubleshoot and address thermocouple-related issues:

  1. Locate the Thermocouple: The thermocouple is a metal rod positioned near the pilot light. It is connected to the gas control valve via a small copper tube.
  2. Clean the Thermocouple: Over time, the thermocouple can accumulate dirt, soot, or residue, which can affect its ability to sense the pilot flame accurately. Gently clean the thermocouple using a soft cloth or fine-grit sandpaper to remove any buildup. Be cautious not to bend or damage the thermocouple during cleaning.
  3. Check the Thermocouple Connection: Ensure that the thermocouple is securely connected to both the gas control valve and the pilot assembly. Tighten any loose connections if necessary. A loose connection can disrupt the thermocouple’s ability to detect the pilot flame and may result in the pilot light not staying lit.
  4. Check the Thermocouple position: Improper positioning or a bent thermocouple can prevent it from sensing the pilot flame correctly. Verify that the thermocouple is properly aligned and extends into the flame.
  5. Test the Thermocouple: You can perform a simple test to check the thermocouple’s functionality. Hold down the pilot button or control knob to manually ignite the pilot light. Once the pilot light is lit, continue holding the button or knob for about a minute to allow the thermocouple to heat up. If the pilot light remains lit after releasing the button, it indicates that the thermocouple is functioning correctly. However, if the pilot light goes out when you release the button, it suggests a faulty thermocouple that needs to be replaced.

Problem 5: Faulty Thermal Cut Off switch (TCO)

If your thermopile is functioning properly, the next component to investigate is the thermal cut-off switch. When the thermal cut-off switch (TCO) is faulty, it can prevent the pilot light from igniting.

The TCO is wired in series with the thermopile and is designed to cut off power to the valve if the temperature in the combustion chamber becomes too high. A tripped TCO will disrupt the gas flow necessary for lighting the pilot.

Testing continuity of Water Heater thermal shutoff switch using multimeter

To check the continuity of the thermal cut-off switch, you can use a multimeter set to the Ohms setting. Start by disconnecting the wires from the switch and then place the multimeter probes on the switch terminals. If the multimeter displays “OL,” indicating no continuity, it indicates a faulty thermal cut-off switch that requires replacement.

Problem 6: Defective Control Valve

If you’re experiencing problems with your water heater pilot light , one possible cause could be a defective control valve. The control valve regulates the flow of gas to the pilot light and main burner. If the control valve is faulty or malfunctioning, it can disrupt the gas supply and prevent the pilot light from staying lit.

If you suspect a defective control valve, it is recommended to contact a licensed technician or plumber with experience in water heater repairs. They have the expertise and knowledge to diagnose and replace a faulty control valve correctly. They can also ensure that the new control valve is compatible with your water heater model and meets the necessary safety standards.

Preventive Maintenance Tips for Pilot Light Performance:

To maintain optimal performance of your gas water heater’s pilot light, consider the following preventive maintenance tips:

  1. Regularly clean the pilot assembly and surrounding area to prevent the buildup of dirt, debris, or soot.
  2. Check the gas supply and pressure periodically to ensure consistent and adequate flow.
  3. Inspect the thermocouple and thermopile for signs of wear or corrosion, and replace them as needed.
  4. Ensure proper ventilation around the water heater to prevent drafts or inadequate airflow.

By understanding common issues that can arise with gas water heater pilot lights and following the troubleshooting steps provided, you can resolve these problems and maintain the smooth operation of your water heater. Remember to prioritize safety and consult a professional if you’re unsure about performing any maintenance or repairs. Regular maintenance and attention to the pilot light will help prolong the lifespan of your gas water heater and ensure a reliable supply of hot water.

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TanklessHelp Staff

TanklessHelp Staff has an experienced writers and researchers in the field of water heating technology. With a background in HVAC and plumbing, Tanklesshelp staff has in-depth knowledge in many types of waterheaters in America and Canada. They have a passion for educating homeowners and businesses on solving easy to hard repairs and guide them on how to maintain them to save money.

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One Comment

  1. You must look at a component of your water heater’s pilot light to see why it won’t stay lit. This issue typically results from issues with the igniter, solenoid, thermocouple gas control valve, flex tube, pilot tube, or other parts of the gas water heater pilot light.

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