The basic steps to relight a pilot light
To relight a pilot light on a boiler, you need to locate the pilot assembly (usually a small tube near the burner), turn the gas control knob to the "Pilot" or "Off" position, hold a lit match or lighter to the pilot opening for 30 seconds while pressing the ignition button, then turn the knob back to "On" once the flame catches. The whole process takes about a minute if the gas is flowing and the igniter works.
Most modern boilers have a piezo igniter (a button you press) rather than requiring an external flame, but the principle is the same: you are introducing a spark or flame to the gas jet while gas flows to that point. If the pilot does not light after three attempts, stop and wait five minutes before trying again — this prevents gas buildup in the combustion chamber.
The pilot light should burn a steady blue flame about half an inch tall. If it lights but goes out when you release the ignition button, the thermocouple (a safety sensor) may not be sensing the heat properly, and you may need a replacement part rather than a relighting.
Key Takeaways
- Turn the gas control knob to "Pilot" or "Off", then hold a flame to the pilot opening while pressing the ignition button for about 30 seconds.
- The pilot flame should be steady and blue; if it goes out when ready after you release the button, the thermocouple may need replacement.
- Wait five minutes between attempts if the pilot does not light on the first try, to avoid gas accumulation in the chamber.
- If you smell gas at any point, stop, leave the area, and contact your boiler service provider or gas company.
Finding the pilot light assembly on your boiler
The pilot assembly is usually mounted on or near the main burner, often inside a small metal box or tube at the base of the boiler. On most residential boilers, it sits to one side of the burner and has a small opening (the pilot jet) where the flame emerges. You may need to remove a front panel or access cover to see it clearly — check your boiler manual for the exact location on your model.
Next to or below the pilot opening, you will find the gas control knob (labeled "On," "Off," and "Pilot") and usually a button or switch for the igniter. Some boilers have a red or black button you press repeatedly; others have a piezo igniter that clicks when you press it. Familiarize yourself with these controls before you begin, so you are not fumbling in the dark or near an open flame.
What to do if the pilot light keeps going out
A pilot light that relights easily but then goes out within seconds usually signals a faulty thermocouple. This is a thin metal rod that sits in the pilot flame and tells the gas valve to stay open; if it is not sensing heat properly, the valve closes automatically as a safety measure. Thermocouples are inexpensive parts (typically £15 to £40) and are one of the most common boiler repairs.
A pilot that goes out after running for a few minutes may indicate a draft problem — wind or air movement blowing the flame out — or a clogged pilot jet. If you have a draft issue, you may need to shield the pilot or improve ventilation in the boiler room. A clogged jet requires cleaning, which usually means removing the pilot assembly; this is a job for a service engineer unless you are comfortable with small mechanical work.
If the pilot will not light at all, check that the gas supply to the boiler is turned on at the meter or isolation valve. Listen for a hissing sound near the pilot opening when the knob is set to "Pilot" — if you hear nothing, gas is not reaching the pilot, and you need to check the supply line or call your gas provider.
Safety steps before you start
Before attempting to relight the pilot, turn off the boiler at the main switch and wait at least five minutes. This allows any gas that may have accumulated in the chamber to disperse. Never attempt to relight a pilot if you smell gas in the room — open windows and doors, leave the building, and contact your gas company or boiler service provider when ready.
Make sure you have a working lighter or long matches on hand before you begin. A standard lighter works better than short matches because it keeps your hand farther from the flame. If you are using the piezo igniter button instead of an external flame, you do not need a lighter, but test the button first to make sure it is producing a spark.
Wear loose, non-flammable clothing and tie back long hair. Keep the boiler room door open so you have a clear exit if something goes wrong. If you are uncomfortable working near an open flame or gas, contact a may have access to boiler engineer — the cost of a service call is usually less than the cost of an accident.
When to call a professional instead
If the pilot light will not stay lit after two or three attempts, or if you smell gas at any point, stop and contact a may have access to boiler engineer or your gas supplier. Do not keep trying — repeated failed attempts can allow gas to build up in the chamber, creating a safety hazard.
You should also call a professional if the boiler is still under warranty, because relighting the pilot yourself may void the coverage. Most modern boilers have automatic ignition systems that do not require manual relighting, so if your boiler is less than ten years old and the pilot keeps going out, the issue is likely a faulty component that needs professional diagnosis.
If you are renting, contact your landlord or letting agent before attempting any work on the boiler. In most jurisdictions, tenants are not permitted to service gas appliances, and doing so may breach your tenancy agreement.
Troubleshooting: why the pilot light will not light
If you have followed the steps and the pilot still will not light, work through these checks in order. First, confirm that gas is reaching the pilot by listening for a hissing sound at the pilot opening when the knob is set to "Pilot." If you hear nothing, the gas supply is off or blocked — check the isolation valve on the boiler and the meter valve, and make sure both are fully open.
Second, check that the igniter is working. If you are using a piezo button, press it near your ear and listen for a clicking sound; if you hear nothing, the igniter may be faulty. If you are using an external flame, make sure the lighter or match is actually lit before you bring it to the pilot opening.
Third, look at the pilot opening itself. If it appears blocked or clogged with debris, you may need to clean it with a thin wire or needle — but do this only if you are comfortable working with small mechanical parts. If the opening looks clear and gas is flowing, but the flame still will not catch, the igniter or gas valve may need replacement, and you should contact a service engineer.
Frequently Asked Questions
How long should I hold the ignition button down?
Hold the button for about 30 seconds while the flame is at the pilot opening. After the pilot catches, keep holding for another 10 to 15 seconds to allow the thermocouple to heat up and signal the gas valve to stay open. Then slowly release the button — if the flame goes out when ready, the thermocouple is not working properly.
What does a healthy pilot flame look like?
A healthy pilot flame is steady, blue, and about half an inch tall. It should not flicker or change colour. If the flame is yellow or orange, the pilot jet may be clogged with debris, and you should have it cleaned by a service engineer. A flame that is too tall or too short usually indicates a gas pressure issue.
Can I relight the pilot if the boiler is still warm?
Yes, but wait at least five minutes after turning off the boiler before you attempt relighting. This allows the combustion chamber to cool slightly and any accumulated gas to disperse. If the boiler is very hot, wait longer — there is no harm in waiting 10 or 15 minutes.
What should I do if gas is leaking from the pilot assembly?
If you see or smell gas leaking from the pilot assembly itself (not just the normal hissing at the jet), stop when ready, turn off the gas at the meter, open windows and doors, and contact your gas company or a may have access to engineer. Do not attempt to repair a gas leak yourself.
Is it normal for the pilot light to go out during a power cut?
No — a pilot light should stay lit during a power cut because it burns continuously and does not depend on electricity. If the pilot goes out when the power fails, the boiler likely has an electronic ignition system that requires power to function, and you will need to relight it manually once power is restored.