How to Relight a Water Heater’s Pilot Light

The small flame that makes up a pilot light gets its fuel from a tiny stream of gas that enters the water heater through a small tube. The pilot stays lit around the clock, so it can burn up any additional gas released when the water heater turns on.

If the pilot light goes out, the thermocouple or thermopile will not be energized and the pilot safety valve will open. Gas will stop flowing to the pilot burner and the water heater shuts off. Electronic ignition systems protect against those risks by using built-in flame sensors to detect whether burners are lit before gas flows through the heater. If the burner doesn’t ignite automatically after several attempts, the heater can go into “lockout mode” to help prevent gas buildup.

Traditional/Manual

Traditional or standard pilot lights have flames that burn 24/7. When the water heater comes on, it draws in gas from your home’s gas lines and feeds it through piping to the pilot light. The gas ignites and helps heat the water in the unit’s tank.

While water heaters with a standard pilot light have been viewed as safe and reliable for decades, they do require routine maintenance and regular cleanings to stay functional and operate as safely as possible.

Electronic/Direct Spark

Electronic or direct spark pilot lights rely on an electrical current or a strike against conductive metal to come to life. In units with intermittent pilot lights, this process happens automatically when the water heater kicks on. Sometimes, electronically lit water heaters don’t have a pilot light at all. Instead, they use a hot surface igniter l that comes on when the heater needs to light, and then turns off when the main burner ignites.

There are several reasons a water heater pilot light keeps going out. Understanding the most common causes of pilot light issues can help you come up with a long-term solution, so you can fix your heater and enjoy hot water whenever the need arises.

Gas Pressure Changes

The pilot light on a water heater is susceptible to changes in gas pressure. In most cases, gas pressure will stay constant unless there’s some kind of interference. Even then, the pressure should revert to normal fairly quickly. Relighting your pilot could reset the system, but in some cases, gas pressure becomes an ongoing problem. This typically indicates an issue outside the water heater, perhaps with the external gas lines.

Problems With the Thermocouple/Thermopile

The main job of a water heater’s thermocouple/Thermopile is to power the gas valve and shut down the flow of gas if the pilot light goes out. But if the thermocouple itself is broken the pilot safety valve in the gas valve will not receive power, and the pilot will not remain lit once the pilot knob is released.

Drafts

When investigating a water heater pilot light that won’t stay lit, be on the lookout for drafts that could blow out the pilot light. Sometimes, an open door (if your water heater is in the garage or a utility room that opens to the outside) could be enough to allow a gust of wild to extinguish that small, somewhat fragile flame.

Lack of Combustible Air

Lighting a pilot light on a water heater requires a steady flow of air. If that airflow is limited due to the position of a newly installed water heater or something new blocking an existing unit, the pilot light could struggle to stay lit. For instance, imagine a water heater stuffed into a too-small closet or boxes of leftover yard sale goodies stacked up around the appliance.

Without enough air, it may be impossible for your water heater to properly burn off fuel. That can result in unburned fuel and/or carbon monoxide being released into your home. It’s a dangerous situation. If you suspect a lack of air is causing issues with your pilot light, it’s vital you bring in a tech to consult on moving your water heater or otherwise fixing the airflow issue before you tackle relighting the pilot.

Residual Gas in the Unit

One of the built-in safety systems in modern water heaters is a fail safe that prevents pilot lights from igniting if there is an air flow issue to the water heater.

This is the reason experts instruct homeowners to turn the gas off and let water heaters sit for at least 10 minutes before attempting to relight an extinguished pilot light. Those two steps — shutting off the gas and waiting — allow built-up gas to safely disperse, reducing the risk of an accident.

Ignition System Failure

Electronic ignition systems on gas water heaters are responsible for lighting the pilot light. If that system fails, there’s no fallback mechanism that can save the day. Contact a professional if you have issues with this system.

Clogged Pipes or Kinked Hoses and Tubes

Another possible reason your water heater’s pilot won’t light could be a kink or clog in the flex tubes linking your fuel supply and your gas controller. If those tubes aren’t fully open and operational, the pilot light can’t get the gas it needs to stay lit.

Control Valve Failure

Like any mechanical component integral to the operation of a machine or appliance, the pilot control valve in your water heater can fail over time. If this is the reason behind an extinguished pilot light, you’ll need to call for a service visit, and the valve will most likely need to be replaced.

Most pilot lights can easily be relit at home by a homeowner or other resident, but learning how to relight a pilot light takes time, effort and self-confidence. You also may need to have a certain amount of mobility and flexibility to maneuver around the heater and reach units installed in smaller spaces. If you're unsure about tackling this task on your own, call a certified plumbing contractor to ensure the job is done safely and correctly