The basic steps to turn on most boilers
To turn on a boiler with a pilot light, locate the control knob on the front of the unit — usually labeled with "Off," "Pilot," and "On." Turn the knob to "Pilot" and hold it down while you light the pilot with a long lighter or match near the small opening below the knob. Once the pilot flame appears and stays lit for 30 seconds, release the knob and turn it to "On." The main burner should ignite within a few seconds. If your boiler has an electronic ignition instead of a pilot light, straightforward turn the knob to "On" and the system will light itself automatically.
The exact location of controls varies by boiler model and age. Older units may have the control knob on the side or back of the boiler rather than the front. Check your boiler's manual or the manufacturer's label on the unit itself to confirm the location before you start. If you cannot find the manual, the model number is usually printed on a sticker near the control knob — you can search for it online to find instructions specific to your unit.
Key Takeaways
- Turn the control knob to "Pilot," hold it down, and light the pilot flame with a long lighter or match held near the opening below the knob.
- Once the pilot stays lit for 30 seconds, release the knob and turn it to "On" to ignite the main burner.
- Electronic ignition systems do not require a pilot light — straightforward turn the knob to "On" and the boiler will light itself.
- If the pilot will not stay lit or the main burner does not ignite, check that the gas supply valve is open and the thermostat is set above room temperature.
What to check before you light the pilot
Before you attempt to light the pilot, confirm that the gas supply to the boiler is turned on. Look for a valve on the gas line leading into the boiler — it should be parallel to the pipe when open and perpendicular when closed. If the valve is perpendicular, turn it to align with the pipe. Also check that your home's main gas supply is on at the meter outside or in the basement.
Set your thermostat to a temperature above the current room temperature. If the thermostat is set lower than the actual temperature, the boiler will not fire even if the pilot is lit. Many boilers also have a reset button on the control panel — if the unit has been off for a while or the pilot went out, pressing this button once can help the ignition sequence work properly. Do not press it repeatedly, as this can flood the combustion chamber with gas.
Lighting the pilot light step by step
Turn the control knob slowly to the "Pilot" position. You should hear a faint hissing sound as gas flows to the pilot burner. Hold the knob down firmly — this opens the gas valve and keeps it open while you light the pilot. The knob usually requires continuous pressure; releasing it too early will shut off the gas before the pilot ignites.
Bring a long lighter or long match to the small opening or window below the control knob where the pilot burner is located. You may need to look through a small window or feel for the opening with your hand. Light the pilot and watch for a small blue flame to appear. Once the flame is visible and steady, keep holding the knob down for another 30 seconds to allow the thermocouple — a safety sensor — to heat up and signal that the pilot is burning.
After 30 seconds, slowly release the knob. The pilot flame should remain lit. If it goes out when ready, wait a few minutes for the gas to clear, then repeat the process. If the pilot lights but goes out within a few seconds of releasing the knob, the thermocouple may be faulty and the boiler may need service.
Turning the boiler to "On" after the pilot is lit
Once the pilot flame is stable and you have held the knob for 30 seconds, turn the control knob from "Pilot" to "On." The main burner should ignite within 5 to 10 seconds, producing a larger flame than the pilot. You may hear a clicking sound as the ignition attempts to fire, followed by a whoosh as the burner lights.
Listen and feel for heat coming from the boiler. The unit should begin warming up, and you should feel warmth near the exhaust vent or chimney within a minute or two. If the main burner does not light after turning the knob to "On," turn it back to "Off," wait a few minutes, and try again. Repeated failed ignition attempts can indicate a problem with the gas supply, the ignition system, or the boiler itself.
What to do if the boiler will not stay on
If the pilot lights but goes out when you release the knob, or if the main burner ignites but then shuts off, the thermocouple is likely the problem. The thermocouple is a small safety device that detects the pilot flame; if it is dirty or failing, it will not keep the gas valve open. Try cleaning the thermocouple by turning off the boiler, waiting for it to cool, and gently wiping the tip of the thermocouple with a soft cloth or fine sandpaper. Then attempt to light the pilot again.
If cleaning does not work, or if the boiler lights but the main burner shuts off after a few seconds, the boiler likely needs professional service. A faulty thermocouple, a blocked gas line, or a problem with the control board can all cause this behavior, and these repairs require a technician. Do not attempt to force the boiler to stay on by holding the knob down indefinitely — this can be unsafe and will not fix the underlying issue.
Electronic ignition boilers: no pilot light needed
Newer boilers often use electronic ignition instead of a pilot light. These systems have no open flame and no pilot to light manually. To turn on an electronic ignition boiler, straightforward turn the control knob to "On." The boiler will produce a clicking sound as the ignition sparks, and the main burner will light automatically within a few seconds.
If an electronic ignition boiler does not light, check that the gas supply valve is open and the thermostat is set above room temperature. You may also see a small light on the control panel that indicates the ignition is attempting to fire. If the boiler clicks but does not ignite after several attempts, turn it off and wait 5 minutes before trying again. Repeated failure to ignite usually means the boiler needs service from a technician.
Safety reminders when lighting a boiler
Never use a match or lighter near the boiler if you smell gas. If you detect a strong gas smell, turn off the gas supply at the meter, leave the house, and call your gas company's emergency line. Do not attempt to light the boiler again until a technician has checked for a leak.
Keep the area around the boiler clear of clutter and flammable materials. Make sure the boiler's exhaust vent is not blocked — a blocked vent can cause dangerous gases to back up into your home. If you are uncomfortable lighting the pilot or if the boiler will not stay on after multiple attempts, contact a heating technician rather than continuing to troubleshoot on your own.
Frequently Asked Questions
How long should I hold the control knob down when lighting the pilot?
Hold the knob down for at least 30 seconds after the pilot flame appears. This allows the thermocouple to heat up and signal the gas valve to stay open. If you release the knob too early, the pilot will go out and you will need to start over.
What does it mean if the pilot lights but goes out when I release the knob?
This usually indicates a faulty thermocouple. Try cleaning the tip of the thermocouple with a soft cloth or fine sandpaper, then attempt to light the pilot again. If it still goes out, the thermocouple likely needs to be replaced by a technician.
Can I light the pilot with a regular match instead of a long lighter?
A long lighter is safer because it keeps your hand farther from the flame and the boiler. A regular match can work, but you risk burning your fingers. If you use a match, light it first, then hold it near the pilot opening while holding the control knob down.
Why is my boiler not igniting even though the gas is on?
Check that your thermostat is set above the current room temperature — the boiler will not fire if the thermostat is set lower. Also confirm the gas supply valve on the boiler itself is open (parallel to the pipe). If both are correct, the ignition system or gas line may be blocked and will need professional inspection.
Is it normal to hear clicking sounds when the boiler ignites?
Yes, clicking is the sound of the ignition sparking. You should hear it for a few seconds before the burner lights. If you hear clicking for more than 10 seconds without the burner igniting, turn the boiler off and wait before trying again.