The basic steps to relight your boiler pilot

Relighting a boiler pilot is a straightforward process you can do yourself in most cases. First, locate the pilot light assembly on your boiler — it is usually a small tube or burner near the main burner, often at the bottom front of the unit. You will see a small ignition button (sometimes labeled "Ignite" or "Pilot") and a control knob marked with settings like "Pilot," "On," and "Off."

Turn the control knob to the "Off" position and wait five minutes. This clears any unburned gas from the chamber. Then turn the knob to "Pilot." Press and hold the ignition button while holding a long lighter or lit match near the pilot opening. You should see a small blue flame appear within a few seconds. Keep holding the button for 30 to 60 seconds after the flame appears — this allows the thermocouple (a safety sensor) to heat up and stay engaged.

Once you release the button, the flame should stay lit. If it goes out when ready, wait five minutes and try again. If it still will not stay lit after two or three attempts, the thermocouple may need replacement — that is a job for a heating technician.

Key Takeaways

  • Turn the control knob to "Off" and wait five minutes before attempting to relight the pilot.
  • Switch the knob to "Pilot," press the ignition button, and hold a flame near the pilot opening until you see a small blue flame.
  • Keep the button pressed for 30 to 60 seconds after ignition so the thermocouple heats up and holds the flame steady.
  • If the pilot will not stay lit after two attempts, the thermocouple is likely faulty and requires a professional to replace.

Why your pilot keeps going out

A pilot that lights but then extinguishes within seconds usually points to a thermocouple problem. The thermocouple is a small metal rod that sits in the pilot flame and generates a tiny electrical signal telling the gas valve to stay open. If it is dirty, corroded, or failing, it cannot hold that signal, and the valve closes.

Before assuming the thermocouple is bad, clean it first. Turn off the boiler, wait for it to cool, and gently wipe the tip of the thermocouple with a soft, dry cloth or fine steel wool. Dirt and soot buildup can block the heat from reaching the sensor. Relight the pilot and hold the button for the full 60 seconds — sometimes a cleaned thermocouple will work again.

If cleaning does not help, the thermocouple has likely reached the end of its life. Replacement typically costs between $150 and $300 in parts and labor, depending on your boiler model and your region. A heating technician can diagnose this in one visit.

When to call a professional instead

Do not attempt to relight the pilot if you smell gas. Leave the house, call your gas company's emergency line from outside, and wait for them to inspect the boiler. A gas smell near the pilot area usually means a leak in the gas line or valve, which is dangerous and requires professional repair.

Also call a technician if the pilot lights but the main burner does not ignite after you turn the knob to "On." This suggests a problem with the main gas valve or the ignition system, not the pilot itself. Trying to force the main burner to light can waste gas and create a safety hazard.

If your boiler is more than 15 years old and the pilot keeps going out even after thermocouple replacement, the boiler itself may be nearing the end of its useful life. A technician can tell you whether repair or replacement makes more sense for your situation.

What to do if you cannot find the ignition button

Some older boilers do not have an electric ignition button. Instead, they use a piezo igniter — a small button you press repeatedly to create a spark. Press it 3 to 5 times in quick succession while holding a lighter or match near the pilot opening. You should see a spark and then a flame.

If your boiler has neither an electric button nor a piezo igniter, you will need to use only a long lighter or long match to light the pilot manually. Hold the flame steady near the pilot opening for 10 to 15 seconds until the pilot catches. This method is less convenient but works reliably.

Check your boiler's manual if you are unsure which type you have. The manual usually includes a diagram showing the exact location of the ignition controls and the correct sequence for relighting. If you no longer have the manual, search online for your boiler's make and model number — most manufacturers post PDFs for free.

Safety checks before you relight

Before you touch anything, make sure the area around the boiler is clear of clutter and that you have good ventilation. Boilers need air to operate safely, and a blocked room can lead to carbon monoxide buildup. If your boiler is in a basement or closet, crack a door or window open while you work.

Never relight a pilot if the boiler has been off for more than a few hours in cold weather. In freezing conditions, condensation can collect in the gas line and freeze, blocking gas flow. If this happens, the boiler will not light no matter what you do. Wait for the room to warm up, or call a technician to thaw the line safely.

After you relight the pilot, listen for the main burner to kick in within a minute or two. You should hear a soft whoosh as the main flame ignites. If the main burner does not start, turn the control knob back to "Off" and wait before trying again. Repeated failed attempts to ignite the main burner can flood the combustion chamber with unburned gas.

How to know if the pilot is actually lit

A properly lit pilot flame is small, steady, and blue. It should be about the size of a pea or a grain of rice. If the flame is yellow or orange, the pilot is not burning cleanly — this usually means the thermocouple or burner opening is dirty. Turn off the boiler and clean the thermocouple and pilot opening with a soft cloth.

If you cannot see the pilot flame at all after pressing the ignition button, the flame may be there but too small to see clearly. Some boilers have a viewing window or port; if yours does, look through it in a dimly lit room. You may need to use a flashlight to spot a small blue flame.

Once the pilot is lit and you have held the button for 60 seconds, turn the control knob to "On." The main burner should ignite within 30 seconds. If it does not, turn the knob back to "Off," wait five minutes, and try the whole sequence again from the beginning.

Frequently Asked Questions

How long should I hold the ignition button after I see the flame?

Hold it for 30 to 60 seconds. This gives the thermocouple time to heat up and send a signal to the gas valve to stay open. If you release the button too early, the flame will go out because the thermocouple has not warmed enough yet.

What does it mean if the pilot lights but the main burner won't start?

The pilot is working, but the main gas valve is not opening. This usually means a problem with the valve itself, the ignition system for the main burner, or the control board. This requires a technician to diagnose and repair.

Can I use a regular lighter instead of a long lighter?

A long lighter is safer because it keeps your hand farther from the flame and the hot boiler. A regular lighter works but puts your fingers closer to heat and the pilot opening. If you use a regular lighter, be careful not to touch the boiler or the pilot tube itself.

Is it normal for the pilot to go out if I turn off the boiler for a few days?

Yes. When you turn the boiler off, the pilot light goes out. When you turn it back on, you will need to relight the pilot using the same steps. This is normal and not a sign of a problem.

What should I do if I smell gas while trying to relight the pilot?

Stop when ready, leave the house, and call your gas company's emergency number from outside. Do not use your phone indoors, do not flip light switches, and do not start your car in the garage. A gas smell means a leak that needs professional attention right away.