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Water Heater Pilot Light Won't Stay Lit: 9 Reasons

Before you call out a pro, check out these 9 reasons why your pilot light goes out.

Your water heater pilot light does more than ignite the gas. If your water heater won’t stay lit, it will fail to maintain internal temperature, which lets the water cool. It could also be a sign of a bigger problem.

Sometimes it is fixable with a few simple steps. Here’s what to do when your pilot light won’t stay lit.

Key Takeaways

  • Check for a damaged thermostat or gas valve which could cause inconsistent water temperature.
  • Inspect the thermocouple for obstructions, bends, or damage that may affect the pilot light.
  • Examine the pilot tube and flex tube for blockages or kinks that might restrict gas flow.
  • Seek professional help for faulty main control valves, electrical systems, and burners.

9 Reasons Why Your Water Heater Pilot Light Won’t Stay Lit

Let’s take a look at the most common reasons and what you can do to remedy the situation.

1. Damaged Thermostat or Gas Valve

When you run the hot water faucet, and the water stays cold, you likely have a damaged upper thermostat. If the water runs hot and then goes cold, it is probably a faulty lower thermostat.

Other symptoms include not enough water, and the water takes too long to reheat.

The Solution

Locate the upper and lower thermostats. Check that there is power reaching them using a multimeter. Locate the reset button and press it to reset the thermostats. This determines whether they are operational or faulty.

It may just need a temperature adjustment, which you can do yourself. If nothing makes a difference, you will need to replace the entire thermostat.

Replacing a thermostat will set you back between $100 and $300. It’s also worth factoring in the labor costs of a heating engineer.

2. Obstructed Thermocouple

Thermocouple issues are fairly common. When the pilot light goes out, this is a great place to start your investigation. The thermocouple is designed to pick up an electrical signal from the heat created by the pilot light.

The sensors are highly sensitive and fall foul of dust and dirt particles that block the signal. Even though the pilot light is lit, the thermocouple struggles to detect it, and as a precaution, shuts off the gas supply. It then causes the pilot light to go out.

The Solution

Ensure that the thermocouple is cool to the touch. Grab some sandpaper and gently grind away any built-up dirt and grime. It should fix the issue, but you may need to replace the thermocouple if you still have problems.

If that is the case, it’s time to call in the professionals.

3. Bent Thermocouple

When you examine the thermocouple, check to see that the sensor is the correct distance from the pilot light. A bent thermocouple won’t detect the heat from the pilot light and cut the gas off.

Fixing it is simple enough, but it could be an indication that you need a replacement part.

The Solution

Take a close look at the thermocouple and check that the end of the sensor is in slight contact with the pilot light. If it looks like it is bent, gently it back to the correct position.

4. Damaged Thermocouple

Thermocouples are delicate components inside your water heater. They get clogged with grime and dust, and over time as your unit ages, wear out. The tell-tale signs that you have a damaged thermocouple could be that it malfunctions even though there is no sign of wear and tear or dust build-up.

The Solution

If you suspect bigger problems, check the thermocouple with a multimeter to see if it is functioning correctly. The reading should be above 20MV, which is a millivolt and equivalent to 0.02 volts.

If the reading drops below this threshold, it is damaged and needs replacing. Unless you know what you are doing, your water heater requires the services of a trained technician. Sometimes you have to accept that calling the professionals is the only route.

5. Dirty Pilot Tube

If you have checked your thermocouple and see no signs that it might be the culprit, it’s time to examine the pilot tube. Gas needs to flow freely through the line, so it restricts the flow if it is clogged with dirt and debris.

The Solution

If the tube needs unblocking, grab a needle and clean it out, watching for dirt and debris that might be responsible for causing the blockage. To check your remedy has worked, test the heater and see if the pilot light stays alight.

If it goes out, perform the same task again and then retest.

Top Tip

A healthy flame will be blue.

6. Defective Flex Tube

The flex tube is the main access route for your gas supply. It needs to be free from interruptions to maintain a steady supply. The flex tube can sometimes become twisted or kinked, which slows the gas supply.

If that happens, the pilot light will go out.

The Solution

The good news is it is unlikely to be the flex tube, so make sure you conduct all the other checks that we have mentioned first. Examine the flex tube to see if there are any bends, kinks, or twists.

Straighten it out so that the gas supply flows freely. If you don’t see any kinks and the other checks yield no solution, it might be necessary to replace the entire flex tube.

7. Faulty Main Control Valve

This is the one issue you want to try and avoid. Main control valves are a significant part of your water heater’s internal components, so when it fails, it is expensive to replace. The way to determine if your main valve is at fault is to run through all the checks we have previously mentioned.

Once you have exhausted the process of elimination, the only contender it could be is the main valve.

The Solution

The remedy is the simplest and the most costly. You are unlikely to have the necessary skills to do it yourself, so it’s time to call a professional. The valve needs to be replaced, and that is expensive. Plus, you need to factor in the heating engineer’s labor costs.

8. Faulty Electrical System

Faulty wiring is likely to be the culprit. When the electrical system is wired incorrectly, you get power surges and short circuits that cause the fuses to blow. As a safety precaution, the breaker box shuts down the system, cutting the supply, which causes the pilot light to go out.

The Solution

Much like the main valve, you will have to bite the bullet and call in an electrician. Unless you have the skills and knowledge to complete the task, inexperience and electrical wiring should not mix.

9. Faulty Burner

If you have a faulty burner, it affects ignition, which may cause the pilot light to extinguish. You notice it because when you run the faucet for a few seconds the water gets hot when the burner functions as it should.

If this fails to happen, you probably have a faulty burner.

The Solution

Turn on the faucet and let it run. The water heater should ignite after about 4 seconds, and you hear it fire up. If this fails to happen, try a lower temperature setting. Repeat the process and listen as the boiler ignites.

Again, if it doesn’t fire into life, you will most likely need to replace the burner. This could be costly because you will need the services of a professional.

Investigation Is Vital

Conducting a thorough examination of your water heater to determine the problem is crucial for two reasons: you might be able to fix it yourself, and if you know what the issue is when you call in a professional, you can direct them to the fault.

When a heating engineer charges by the hour, getting the job done swiftly saves you money. It also stops you from falling foul of rogue traders who might try and convince you that the issues are much bigger and you need a completely new water heater.

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About the Author

Mark Weir

Mark spent 24 years working in real estate, so he knows his way around a home. He also worked with contractors and experts, advising them on issues of planning, investments, and renovations. Mark is no stranger to hands-on experience, having renovated his own home and many properties for resale. He likes nothing better than seeing a project through to completion.