The basic steps to light an A.O. Smith pilot light

To light the pilot on an A.O. Smith water heater, turn the gas control knob to "Pilot," hold down the ignition button while holding a lit match or lighter to the pilot burner opening, and keep the button pressed for 30 to 60 seconds after the flame catches. Once the pilot stays lit on its own, turn the gas control knob to "On" or your desired temperature setting.

The whole process usually takes less than five minutes. If the pilot won't stay lit after several attempts, or if you smell gas at any point, stop and call a licensed technician — do not keep trying.

Key Takeaways

  • Turn the gas control knob to "Pilot" before you attempt to light anything, or the gas valve will not release pilot gas.
  • Hold the ignition button down continuously while lighting and for 30 to 60 seconds after the flame appears, so the thermocouple can heat up and signal the valve to stay open.
  • If you smell gas but see no flame after three attempts, turn the knob to "Off," wait five minutes for gas to clear, and call a technician.
  • A pilot light that goes out repeatedly usually means a faulty thermocouple or a draft problem, not a lighting problem.

Locating the pilot light assembly on your A.O. Smith unit

On most A.O. Smith water heaters, the pilot light assembly is at the bottom of the tank, behind or beside the burner chamber. You will see a small metal tube (the pilot burner) and a control knob labeled "Pilot," "On," and "Off." Some models also have a temperature dial or a separate ignition button on the front of the control box.

If your model has an electronic igniter instead of a manual button, you will press a button labeled "Ignite" or see a spark electrode near the pilot opening. Check your water heater's label or manual to confirm which type you have — the steps differ slightly.

What to do before you light the pilot

Before attempting to light the pilot, make sure the area around the water heater is clear of clutter and that you have good ventilation. Open a window or door nearby so any gas that escapes can disperse safely.

Check that you have a working lighter or long matches on hand. A regular short match will not reach the pilot opening safely. If you do not have a long lighter, a long fireplace match or a thin taper candle works well. Do not use paper or cardboard to light the pilot — it will burn too quickly and may not reach the flame opening.

Turn off any other gas appliances in the home, such as the stove or furnace. This reduces the amount of gas in the air and makes it easier to smell if something goes wrong.

Step-by-step lighting procedure

Step 1: Set the control knob to "Pilot." Locate the gas control knob on the front of the water heater's control box. Turn it clockwise until it points to "Pilot." You should hear a faint hissing sound as pilot gas begins to flow.

Step 2: Locate the ignition button. On manual-ignition models, this is usually a red or black button on the control box face. Press it once to make sure it clicks — you may hear a spark or see a small spark near the pilot opening. On electronic models, you may need to press and hold the button.

Step 3: Light the pilot burner. While holding down the ignition button, bring your lit match or lighter to the small pilot burner opening (usually a thin tube pointing downward or to the side). You should see a small blue flame appear within a few seconds. If you do not see a flame after three attempts, stop and wait five minutes before trying again.

Step 4: Keep the button pressed. Once the flame appears, continue holding the ignition button down for 30 to 60 seconds. This allows the thermocouple (a heat-sensing device) to warm up and signal the gas valve to stay open. If you release the button too early, the pilot will go out.

Step 5: Release the button and check the flame. After 60 seconds, release the ignition button. The pilot flame should remain lit. If it goes out when ready, wait five minutes and repeat steps 1 through 4. If it goes out a second time, stop trying and call a technician.

Step 6: Turn the knob to "On." Once the pilot is holding steady, turn the gas control knob to "On" or to your desired water temperature setting (usually marked with numbers or a temperature range). The main burner should ignite within a few seconds, and you will hear a louder flame.

Why the pilot light goes out and won't relight

If the pilot lights but goes out as soon as you release the button, the thermocouple is usually the problem. The thermocouple is a small metal rod that sits in the pilot flame and generates a tiny electrical signal that tells the gas valve to stay open. When it fails, the valve closes even though the pilot is burning. This is not something you can fix yourself — a technician will need to replace it.

A pilot that lights and holds but then goes out after a few hours or days often points to a draft problem. Wind or air currents from a nearby door, window, or vent can blow out the pilot flame. Moving the water heater away from the draft source or installing a draft shield around the pilot opening can help. If the pilot keeps going out in the same spot, ask a technician to check for a faulty thermocouple or a gas valve that is not holding pressure.

If you smell gas but do not see a flame, or if the pilot lights but you smell gas around the unit, turn the knob to "Off" when ready, leave the area, and call a technician or your gas company's emergency line. Do not try to light it again.

When to call a professional instead of lighting it yourself

Call a licensed technician if the pilot will not light after three careful attempts, if you smell gas during or after lighting, if the pilot lights but goes out repeatedly, or if the main burner does not ignite after you turn the knob to "On." These are signs of a thermocouple failure, a gas valve problem, or a gas leak — none of which are safe to troubleshoot on your own.

You should also call a professional if you are not comfortable working near the gas valve, if you have never lit a pilot before and want guidance, or if your water heater is still under warranty. Many warranties require that a licensed technician perform any service work.

Frequently Asked Questions

How long should I hold the ignition button after the flame appears?

Hold it for 30 to 60 seconds. This gives the thermocouple time to heat up and signal the gas valve to stay open. If you release it too soon, the pilot will go out. If you hold it longer, that is fine — it will not hurt anything.

What if I do not have a long lighter or fireplace matches?

A thin taper candle works well and is safer than trying to use a short match. You can also order long fireplace matches online or buy them at most hardware stores. Do not use paper, cardboard, or anything that burns too quickly.

Is it normal for the pilot to go out on its own after I turn the knob to "On"?

No. Once the pilot is lit and you turn the knob to "On," the pilot should stay lit and the main burner should ignite. If the pilot goes out when you turn the knob, the thermocouple or gas valve may be failing. Stop trying and call a technician.

Can I light the pilot if the power is out?

Yes, if your water heater has a manual ignition button (not electronic). If it has an electronic igniter that requires electricity, you will not be able to light it without power. Some newer A.O. Smith models have battery backup for the igniter — check your manual.

What should I do if I smell rotten eggs near the water heater?

That smell is mercaptan, an additive in natural gas that signals a leak. Turn the gas control knob to "Off," leave the area, and call your gas company's emergency line or a technician when ready. Do not light the pilot or use any electrical switches.