How The Pilot Light Works

Have you ever noticed the blue flame in your boiler – that is the pilot light.

pilot light

The pilot light is a small gas flame that ignites a more powerful gas burner. Typically, that flame lights continuously. Today, only older boiler models, those that use natural gas, or fireplaces that use gas logs, have pilot lights. Other gas appliances that use pilot lights are furnaces, water heaters, hobs and gas ovens.

How does the pilot light work?

Pilot lights are basically valves that provide the flame needed to light the gas that comes out of the main burner. A small amount of lighted, continuously burning gas passes through it. When the boiler is turned on, another valve releases gas into the burner and the pilot light ignites that gas.

Identifying pilot lights

If you are not sure whether your boiler operates using one, look at the power switch of your boiler. There is likely a “pilot” position for the switch if the appliance uses a pilot light. You can also check the panel where the gas burner is. When you open the panel, you should see the small blue flame visibly.

Pros and Cons of Using Pilot Lights

Pilot lights do not require electricity to operate, so most appliances that use pilot lights will operate during a power outage. Because pilot lights are always burning, they offer instant ignition to the main burner.

One of the downsides of using pilot lights is the waste of gas. In the US, 20% of gas used annually is for pilot lights alone.


In the event the the pilot light goes out, there is a valve attached to the pilot light tube that acts as a sensor. It will be able to tell whether the pilot light is lit or not, and in case the light blows out, it will stop the tube from blowing gas – that can potentially collect inside the home and ignite, resulting to a fire or explosion. A thermocouple is used here to detect whether the pilot light is lit or not, without needing any form of electricity from outside. The thermocouple uses heat from the pilot light flame to generate its own electricity.

Common Problems

If your pilot light won’t stay on, you can solve the issue yourself by following our tips: Pilot Light Keeps Turning Off.

For other pilot light issues, call RJ Gas and our engineers will be happy to check your boiler for you.


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