Whether it's on your boiler, water heater, or furnace, a pilot light that won't stay lit can be a major problem. With gas-powered appliances, the pilot is a necessary part of the system, without which it won't run. Fortunately, most pilot light issues are an easy fix once you know the cause of the problem.
Dirt and Dust
One of the most common reasons for a constantly failing pilot light is dirt and dust on the pilot opening or the tip of the pilot gas valve. You can usually spot a dirt problem by watching the flame when it is lit. It may appear to flicker or there may even be small sparks as small dust motes ignite briefly. In the case of a clogged fuel nozzle, the flame may also appear to burn yellow or orange instead of blue-white, simply because there is insufficient fuel to burn as hot as it should. Turn off the system and the gas supply, then thoroughly clean the opening and valve. You can use a small needle to unclog the valve, if necessary.
Location matters when it comes to a gas appliance. Overly small appliance closets are a common problem, particularly for water heaters since they are often shoved into small utility closets. These small spaces have insufficient airflow, so the pilot light may actually go out because of too little oxygen. Installing a vent in the small closet can help. Appliances located near a draft can also have pilot light issues, as the draft may constantly blow out the light. You may need to seal windows or doors, or even install a partition, in order to block the draft so it doesn't affect your pilot light.
The thermocouple is a very important safety feature on gas HVAC appliances. It shuts down the gas supply in the event the pilot light goes out. In some cases, though, it may malfunction and shut down the gas even if the pilot is still burning. The most common reason is that the thermocouple has become bent or misaligned, so it is no longer sensing the pilot light as it should. In some cases, it may malfunction simply because it is dirty and needs to be wiped clean. Another cause of a malfunction is if the sensor inside of the thermocouple fails, which means it is time to replace it.
Contact an HVAC repair service for more help if your pilot light isn't remaining lit.