The Basic Steps to Light Your Boiler

To light a boiler pilot light, you will turn the gas control knob to the "Pilot" position, hold a lit match or lighter near the pilot burner opening, and press the ignition button while the flame catches. Once the pilot flame is steady and blue, you will turn the knob to "On" and wait a few minutes for the main burner to ignite. The whole process takes about two minutes if the gas is flowing and the spark igniter works.

Most modern boilers have an automatic ignition button you press while holding a flame near the pilot opening. Older models may require you to light the pilot manually with a match while pressing the button. Either way, the goal is the same: get a small blue flame burning at the pilot burner, which then signals the gas valve to open and light the main burner.

Key Takeaways

  • Turn the gas control knob to "Pilot," hold a lit match or lighter at the pilot opening, and press the ignition button until the flame catches.
  • The pilot flame should be blue and steady; if it is yellow or orange, the burner may be dirty and needs cleaning.
  • Once the pilot is lit, turn the knob to "On" and wait two to three minutes for the main burner to light automatically.
  • If the pilot will not stay lit after you release the button, the thermocouple (a safety sensor) may be faulty and needs replacement.

Locating the Pilot Light and Gas Control Knob

Open the boiler access panel or door—usually held by a single screw or clip—to see the pilot burner and gas control knob. The knob is typically a round dial on the front of the gas valve, labeled with three positions: "Off," "Pilot," and "On." The pilot burner itself is a small opening, usually brass or steel, positioned below or beside the main burner assembly.

If you cannot find the pilot light, check your boiler manual or look for a label on the boiler itself that shows the location. Some boilers have the pilot assembly tucked behind a secondary panel. Do not force any panels open; if you cannot access the pilot safely, call a technician rather than risk damaging the boiler or gas line.

Preparing to Light the Pilot

Before you begin, make sure the gas supply to the boiler is on. Check that the main gas valve (usually a lever handle on the gas line leading to the boiler) is in the open position—the handle should be parallel to the pipe, not perpendicular. If the valve is closed, turn it open slowly and wait 30 seconds for gas to reach the pilot burner.

Gather a long lighter or long matches before you start. A regular match or short lighter makes it harder to reach the pilot opening safely without burning your hand. If you have neither, a thin piece of rolled paper lit from a stove burner will work in a pinch, though a lighter is safer and more reliable.

Lighting the Pilot Step by Step

Turn the gas control knob to the "Pilot" position. You should hear a faint hissing sound as gas flows to the pilot burner. Hold your lit match or lighter about half an inch from the pilot opening—close enough for the flame to reach it, but not so close that you burn your hand. Press and hold the ignition button (usually a red or black button near the knob) while the match or lighter flame is near the opening.

Keep the button pressed for 10 to 15 seconds after you see the pilot flame ignite. This allows the thermocouple—a safety sensor that detects the pilot flame—to warm up and signal the gas valve to stay open. If you release the button too soon, the pilot will go out. Once the flame is steady and blue, slowly release the button. The pilot should stay lit on its own.

If the pilot goes out as soon as you release the button, press it again and hold for a full 20 seconds. If it still will not stay lit, the thermocouple is likely worn out and needs replacement by a technician. Do not keep trying to light it repeatedly; this wastes gas and can create a safety hazard.

Turning the Boiler On After the Pilot Is Lit

Once the pilot flame is steady and blue, turn the gas control knob from "Pilot" to "On." You should hear the main gas valve open with a soft click. Wait two to three minutes for the main burner to ignite automatically. You may see a spark or hear clicking as the ignition system tries to light the burner. The main flame should be blue and even across all burner ports.

If the main burner does not light within three minutes, turn the knob back to "Off," wait five minutes for any unburned gas to clear, and try again. If it still will not light after a second attempt, stop and call a technician. Repeated failed ignition attempts can allow gas to build up in the combustion chamber, which is a safety risk.

What the Pilot Flame Should Look Like

A healthy pilot flame is blue with a small yellow tip—usually about half an inch tall. The flame should be steady and not flicker or dance. If the flame is mostly yellow or orange, the pilot burner opening is clogged with dust or debris. A yellow flame also burns cooler and may not heat the thermocouple enough to keep the gas valve open.

If the flame is yellow, turn the knob to "Off" and let the boiler cool for 10 minutes. Then use a thin needle or straightened paperclip to gently clear the pilot opening. Be very careful not to damage the opening or the thermocouple. Light the pilot again; the flame should now be blue. If it is still yellow after cleaning, the burner may need professional cleaning or replacement.

Common Mistakes and How to Avoid Them

The most common mistake is releasing the ignition button too soon. Many people press it for only a few seconds, see the flame light, and let go—only to watch it go out when ready. The thermocouple needs 10 to 20 seconds of heat to work properly. Press and hold the button for the full time, even after the flame is clearly lit.

Another mistake is trying to light the pilot when the main gas valve is closed. If you hear no hissing sound when you turn the knob to "Pilot," check the main gas valve on the supply line. It should be open (handle parallel to the pipe). If it is closed, open it slowly and wait 30 seconds before trying to light the pilot again.

Do not use a match or lighter with a very short flame, and do not try to light the pilot from below or at an awkward angle. Position yourself so you can see the pilot opening clearly and bring the flame straight toward it. If you cannot reach it comfortably, use a longer lighter or ask someone to help hold the boiler panel open while you light it.

Frequently Asked Questions

What if the pilot light keeps going out after I turn the boiler on?

A pilot that lights but will not stay lit usually means the thermocouple is failing. This safety sensor detects the pilot flame and signals the gas valve to stay open. If it is worn out, it cannot send the signal, and the valve closes. You will need a technician to replace the thermocouple, which is a straightforward repair that takes 30 minutes to an hour.

Can I light the pilot if the boiler is still warm?

Yes, but wait at least 10 minutes after the boiler shut off before you try. If the boiler is very hot, the thermocouple may already be warm enough to keep the gas valve open without you holding the button. Let it cool slightly so you can control the process and make sure the pilot stays lit for the right reason.

Is it safe to light the pilot myself, or should I call a technician?

Lighting the pilot is safe if you follow the steps carefully and the boiler is in good working order. However, if the pilot will not light after two attempts, if you smell gas, or if you are not comfortable working with the boiler, call a technician. Do not keep trying repeatedly, as this can create a safety hazard.

What does it mean if I see a yellow or orange flame instead of blue?

A yellow or orange pilot flame means the burner opening is clogged with dust or soot. Turn off the boiler, let it cool, and use a thin needle to gently clear the opening. If the flame is still yellow after cleaning, the burner may need professional cleaning or the thermocouple may need adjustment by a technician.

How long should I hold the ignition button down?

Hold the button for 10 to 20 seconds after you see the pilot flame ignite. This gives the thermocouple time to heat up and signal the gas valve to stay open. If you release it too soon, the pilot will go out. If you hold it longer, that is fine—just do not release it before the flame is clearly steady and blue.