Water Heater Pilot Light Won't Light

Start with the lighting steps on the tank

Many failed lights are a technique problem. The instructions are on the label on the front of the heater, and they beat any general guide, this one included. The short version for a standing-pilot tank with a push-button igniter:

1. Turn the gas control knob to OFF and wait 10 minutes so any gas in the burner area clears.
2. Turn the knob to PILOT and push it all the way in. A.O. Smith says it should travel about ¼ inch.
3. Hold it down and press the igniter. On A.O. Smith's piezo models the manual says to click it rapidly 4 to 5 times.
4. Still nothing after two tries? Let go of the knob and wait ten minutes before you try again.

The step people skip is holding the knob fully down. Bradford White's service manual lists a pilot button that isn't fully depressed as its own cause, with the fix "fully depress pilot lighting button". Our full walkthrough is on how to light a water heater pilot light.

A brand-new heater, or one that's been off for a while, can also take several attempts while air bleeds out of the gas line. That's normal. Stay patient but keep the ten-minute waits.

Likely causes

1. 1

   Cause 1: No gas getting to the heater

   Check the shutoff valve on the gas line next to the heater. The handle should run parallel to the pipe. Then try another gas appliance. Lennox's advice is simple: if the stove or furnace won't light either, the problem is upstream, and you call your gas provider. On propane, look at the tank gauge. An empty tank looks exactly like a broken water heater.

   Bradford White's first step for a pilot that won't light is to turn on the gas supply and check line pressure. Measuring pressure needs a manometer and belongs to a technician. You can at least confirm the valves are open.

2. 2

   Cause 2: The igniter isn't sparking

   Dim the room lights and watch through the sight glass while you click the igniter. A.O. Smith's manual uses that exact test. No spark usually means the igniter wire has slipped out of its connector. Push it firmly back into the white connector and try again. If there's still no spark, the piezo button itself may be worn. You can also light most standing pilots with a long lighter, as A.O. Smith's FAQ notes. See our water heater igniter page for the rest.

3. 3

   Cause 3: A clogged or kinked pilot tube

   You see a good spark and you're sure gas is on, but nothing catches. The pilot tube or orifice may be blocked. Lennox puts this down to dust or mineral buildup cutting off gas flow, and A.O. Smith lists a clogged or kinked gas tube among the main reasons a pilot won't light. Bradford White's fix is to clean, repair or replace the obstructed tube or orifice.

   On a sealed-combustion heater this means pulling the burner assembly and breaking the seal on the inner door. If you've never done it, hand it to a plumber. A torn gasket on that door defeats the flammable vapor protection.

4. 4

   Cause 4: A failed gas control valve or ignition system

   If gas is on, the spark is good and the tube is clear, the gas control valve is next. A.O. Smith says a failed control valve usually needs service and likely replacement. On models with electronic ignition, the status light tells you a lot. It should flash once per second once the pilot is lit. If it doesn't flash after three attempts, go to the "Troubleshooting No Status Light" section of your owner's manual. More on that part on our gas control valve page.

5. 5

   Cause 5: The flammable vapor system has shut it down

   Tanks built with FVIR (flammable vapor ignition resistance) have a resettable thermal switch, and the manual is blunt: don't disable or modify it. If gasoline or solvent fumes got to the flame, A.O. Smith says the flame arrestor shows discoloration and the whole heater must be replaced. The same goes for a heater that sat in flood water. If either applies, don't keep trying to light it.

A.O. Smith pilot will not light

A.O. Smith owners get two specific notes from the manual. First, if the pilot lights but the damper linkage at the inlet doesn't move, the causes range from low gas pressure at the actuator to a frozen damper door, and every one of them is a service call. Second, if the knob doesn't pop back up after you release it, stop and call a technician or the gas supplier right away.

When to stop and call a plumber

Stop and call if:

• you smell gas at any point
• the pilot still won't catch after the gas, spark and tube checks
• you'd need to open a sealed burner door
• the heater has been flooded or exposed to fumes

HomeGuide's 2026 cost guide puts a pilot light replacement at $50 to $200 and an igniter replacement at $75 to $350. If it turns out to be the gas control valve, expect $150 to $550. Many plumbers also charge a $50 to $200 service call fee. Our water heater repair cost page breaks down the rest.