AO Smith Gas water heater Parts — Browse All Models

What to do when the pilot won't stay lit on your AO Smith gas water heater

If your pilot light will not stay lit, it is important that you take steps to fix it immediately. Several problems can shut off the pilot-a failed gas supply, lack of combustion air due to a clogged vent or a vent draft that blows out the pilot. A missing, crooked or blocked vent draft hood can cause a vent draft. Also, if the vent pipe cap on the top of the vent pipe on the roof is blocked or missing, wind can go down the pipe and blow the pilot out.

Another common problem causing the pilot to go out or not stay lit is a failed thermocouple (pilot generator). The thermocouple in your water heater keeps the pilot lit by sending a low current electrical signal to keep the gas valve open. If the thermocouple fails, it doesn't send the signal to the gas valve and the gas valve shuts off, extinguishing the pilot.

When lighting the pilot, you press and hold the pilot button to supply gas to the pilot until the pilot heats up enough to generate the signal to keep the gas valve open on its own. If the pilot light goes out when you release the button, you'll likely need to replace the thermocouple because it isn't sending the signal to the gas valve to keep the gas valve open.

Common AO Smith gas water heater replacement parts

• Burner assembly. The burner assembly fits below the tank in a gas water heater. Controlled by a thermostat, the burner assembly heats the water in the tank.
• Drain valve. The drain valve fits at the bottom of the tank and allows you to drain water from the tank.
• Temperature-pressure relief valve. The temperature-pressure relief valve (T&P) is a safety device attached to the side of the tank. If a thermostat fails, water inside the tank overheats and builds up pressure that can damage the tank and tank fittings. The T&P valve opens automatically and discharges water to relieve pressure if excessive pressure builds up in the tank.
• Thermocouple. The thermocouple detects whether your pilot light is on by generating a very small electrical current powered by the heat of the pilot flame. If the gas valve assembly doesn't sense the small electrical current provided by the thermocouple, or the thermocouple cools, it assumes that the pilot light is off and shuts down the gas.