Water heater pilot light won’t stay lit after replacing thermocouple

Water heater pilot light won’t stay lit after replacing thermocouple. The water heater is used to boil water in the winter for various household purposes like washing dishes in the kitchen and bathing in the bathroom.

All parts are very important, but the water heater pilot is the most useful element because it connects the burner and the gas valve.

If the water heater pilot is working properly, it will ensure that the flame is continuously lightening in the water heater.

With time different heater elements become faulty due to worn out, so if your water boiler pilot won’t stay lit even after replacing the thermocouple, first of all, shut off the gas supply and check the gas control valve because there are chances that it is faulty due which the water heater pilot won’t stay lit.

It seems like the gas valve failed to pass the gas to the pilot. Please read this guide to learn about other causes of this problem and how to troubleshoot them.

Water heater pilot light won’t stay lit after replacing thermocouple

A gas water heater usually works on a gas supply, whether it is natural gas supply or a gas tank, to warm the water, but it also requires some electric power to work.

If your water boiler pilot doesn’t stay lit after changing the thermocouple, then don’t worry because it’s not difficult to know which element is the culprit, whether it is an issue with the natural gas supply or its electrical error.

If you have some basic tools and skills, keep reading to fix the problem.

Check the gas supply

check the gas supply

If your water heater pilot is not igniting after changing the thermocouple, then the first thing to ensure is the gas supply.

If you use a gas tank, then check the gas gauge to know the remaining gas in the tank.

You can also make an idea from pinking up the gas tank. If you easily pick up the gas tank, it means it is empty, and it’s time to refill the gas to turn on the water heater.

If your water heater is connected to natural gas supply pipelines, then contact them to know about the low gas pressure.

You can also make an idea by turning on the kitchen stove to check the gas pressure in the home.

Gas control valve is defective

gas control valve is defective

The gas control valve is the most important element in boiling the water in the water heater because it controls the gas flow in the main pipeline.

If the gas pressure is very high, it manages it and allows the gas at a suitable pressure to flow toward the water heater.

If there is no issue with the gas control valve and it is functioning well, you can easily light the pilot because it heats the thermocouple, which helps the burner warm the water.

But, if the control valve is faulty and is not doing, it will not light up the pilot to ignite. So, check the gas control valve because it is not opening and releasing the gas to lit the pilot after replacing the thermocouple.

If you are skillful, replace the gas valve; otherwise, contact a gas plumber to repair or change the defective gas control valve.

Water heater pilot is dirty

water heater pilot is dirty

If you recently replaced the thermocouple in the water heater and its pilot won’t light now, check the area around the burner.

Most people ignore the water heater for a long time and do not clean all its parts, due to which junk and debris gather on its elements, affecting the unit’s functioning.

If your pilot is dirty due to carbon particles and smoke, the pilot burner will lose its performance.

If the heater pilot is not working as it usually does, it becomes tough for the pilot light to stay lit. So, if the heater pilot won’t light, you can hot warm the water in the boiler.

So, you have to keep cleaning the debris from the pilot and its surrounding area with a wide-bristled brush. Hopefully, the pilot will light up after cleaning the debris from the pilot and pilot tube.

The pilot tube is blocked

The pilot tube consists of a pilot orifice that must be clean from dust and debris for rapid gas flow. If this pilot tube becomes clogged, then it stops the gas flow, due to which the pilot won’t light up.

If, unfortunately, the thermocouple or any other element becomes faulty and you need to replace that defective part, clean the carbon particles and debris from other parts to maintain the appliance.

If you do not clean your water heater for a long time, then the pilot tube is clogged with debris, and if it becomes clogged, it affects all the functioning of the water heater because the gas flow becomes slow or stopped due to blockage.

There is no need to call someone to unclog the pilot tube because you can easily clean the clogged tube in ten minutes if you just know how to unmount the screws.

  • Open the water heater cover to get access to the pilot orifice.
  • Unmount the pilot orifice screws.
  • Take a small amount of alcohol in a cup.
  • Dip a soft sponge or clean cloth in the alcohol and scrub it at all parts of the pilot tube to clean all the dirt and sludge.
  • If the cloth does not reach deep in the pilot tube, you can use a match stick or toothpick to clean any junk.
  • After cleaning the debris, put back all the things in their original positions and clean the area.
  • Take a match stick and hold down the control knob to light the pilot.
  • If this is the issue, your water heater pilot will ignite.

Thermocouple not installed properly

thermocouple not installed properly

If the water heater pilot won’t stay lit after replacing the thermocouple, then it is also possible that you have not installed the thermocouple accurately in the water heater.

It is suggested do you that do not try to repair or replace any faulty component in any electrical appliance unless you are professional because a slight mistake or fault can lead to a big disaster and may increase the damage.

However, if you have installed the thermocouple in the water heater, then recheck all the elements and screws are properly positioned or if any screw is missing.

First of all, it’s necessary to buy an actual thermocouple that matches the original element, so always take away the faulty component with yourself at the hardware store to match the new element with the original.

Reinstall the new thermocouple in the water by keeping its wire straight; otherwise, it will not function, and the heater pilot will not switch on.


The final thoughts in this guide are I almost covered all the possible causes of why a heater pilot won’t stay lit after replacing the faulty thermocouple.

Keeping the water heater pilot and pilot tube clean using a wide-bristled brush is essential, and there should be no mess and debris on these elements.

Check the gas control valve because it is the main element that manages the gas glow in the water heater. If this valve becomes faulty, immediately change it with a new one to ignite the pilot.

I am hopeful this guide helped you to fix the problem; however, if still, the heater pilot is not lightning, then contact a skillful professional for deep inspection.

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