The Pilot on My Gas Boiler Does Not Want to Turn On

Clogged Orifice

• If your pilot light doesn’t light at all, the orifice may be clogged. If the pilot lights, but keeps going out, you may have a partial clog. Remove the burner to the water heater and unscrew the pilot line from the pilot head. The orifice is found at the end of the pilot supply line. Inspect the orifice by holding it up to a light and looking through the tiny hole where the gas passes through. Tap the orifice, or blow through it, to remove the clog. You should also inspect the pilot supply line for kinks and blow through it to ensure there aren’t any clogs. Reinstall the orifice, pilot tube and burner assembly and try lighting the pilot. If the pilot still doesn’t light, the problem may be with the gas control valve.

Valve

• The gas control valve is responsible for controlling the pilot light and the water temperature. The short probe on the back of the valve is the high limit probe and it’s responsible for shutting down the gas flow if the thermostat stops working. The long temperature probe turns the gas valve on and off depending on the temperature setting. You must replace valves that malfunction; they can’t be repaired. This is considered a major repair and you will probably have to call a licensed plumber to do it.

Thermocouple

• Sometimes the pilot will light, but it won’t stay lit. If this happens to your hot water heater, you may have a problem with the thermocouple. The thermocouple is a safety device that tells the gas valve to remain closed if the pilot light is out. Try relighting the pilot. If it lights, but the flame goes out when you release the button, then you may need to replace the thermocouple or the thermostat. A licensed plumber can check the thermocouple for you.

Drip Leg

• The drip leg is a piece of pipe that’s designed to collect sediment that may clog the flow of gas through the line. It’s a piece of pipe on the main gas line just before it enters the heater and you can recognize it because it runs downward from the line. Sometimes the drip leg corrodes and blocks the flow of gas. This will cause the pilot light to go out. Replace the drip leg to correct this problem.

Drafts

• Sometimes pilot lights won’t stay on because there’s a draft in the room or because there’s a nearby fan that keeps blowing it out. Protect the pilot light with a downdraft hood on top of the tank and a pilot light baffle near the bottom.