Starting Your A.O. Smith Water Heater

To turn on an A.O. Smith water heater, locate the gas control valve on the front of the tank—it has a dial with three positions: Pilot, On, and Off. Turn the dial to Pilot, hold it down for 30 to 60 seconds while you light the pilot with a long lighter or match, then release. Once the pilot stays lit, turn the dial to On. If you have an electric model, straightforward flip the breaker switch to the On position at your electrical panel.

The exact steps depend on whether your heater uses gas or electricity, and whether the pilot light has gone out or you are starting a brand-new unit. Both types are straightforward once you know where to look and what each control does.

Key Takeaways

  • Gas models require you to hold the control valve on Pilot while lighting the pilot flame with a lighter or match, then switch to On once it stays lit.
  • Electric models have no pilot light—you only need to switch the breaker at your electrical panel to the On position.
  • If the pilot will not light after 60 seconds, release the valve, wait five minutes, and try again to avoid flooding the combustion chamber with gas.
  • A clicking sound at the pilot igniter is normal; a complete absence of any sound or smell of gas may mean the gas supply is shut off at the meter.
  • Once the heater is on, water takes 30 to 45 minutes to heat to full temperature on first startup.

Gas Water Heater Startup Steps

Stand in front of your A.O. Smith gas water heater and locate the control valve on the lower front of the tank. The valve has a round dial with three labeled positions: Off, Pilot, and On. Turn the dial clockwise to Pilot—you will feel it click into place.

Hold the dial down firmly in the Pilot position and use a long lighter or long match to ignite the pilot opening just below the dial. You should see a small blue flame appear within a few seconds. Keep holding the dial down for another 30 to 60 seconds after the flame appears. This allows the thermocouple (a safety sensor) to heat up and signal that the pilot is burning.

Release the dial and turn it to On. The main burner should ignite with a whoosh sound. If it does not, turn the dial back to Off, wait five minutes, and repeat the process. Do not hold the dial down for more than 60 seconds on your first attempt—this can flood the combustion chamber with unburned gas.

Electric Water Heater Startup Steps

Electric A.O. Smith water heaters have no pilot light or gas valve. Instead, they are controlled by a breaker switch at your home's electrical panel. Locate your panel (usually in a basement, garage, or utility closet) and find the breaker labeled for the water heater—it is typically a double-width breaker rated for 30, 40, or 50 amps.

Flip the breaker switch to the On position. You may hear a soft click as it seats. The heater is now on and will begin heating water when ready. There are no additional steps. If the breaker trips back to Off on its own, turn it back on once and wait 24 hours—if it trips again, the heating element may be failing and you should contact a technician.

What to Do If the Pilot Will Not Light

If you follow the steps above and the pilot flame does not appear, first check that gas is reaching the heater. Look at the gas meter outside your home—if the dial is not moving when you turn the dial to Pilot, the gas supply may be shut off at the meter or at a valve between the meter and the heater. Check for an inline shut-off valve on the gas line leading to the heater and make sure it is turned parallel to the pipe (open position).

If gas is flowing but the pilot still will not light, listen for a clicking sound near the pilot opening when you hold the dial on Pilot. A steady clicking means the electronic igniter is working. If you hear clicking but no flame, the pilot opening may be clogged with dust or debris. Turn the dial to Off, wait five minutes, and try again. If the clicking stops or you hear nothing at all, the igniter may need replacement—contact an A.O. Smith service technician or a licensed plumber.

Do not attempt to light the pilot with the dial on On—this is unsafe and can cause the main burner to ignite unexpectedly. Always use Pilot position when lighting by hand.

Checking Water Temperature After Startup

After you turn the heater on, it will take time to heat the water in the tank. On first startup, expect 30 to 45 minutes before hot water reaches your taps. On a gas heater, you can see the main burner flame through the small window on the front of the tank—if it is burning steadily, the heater is working.

The thermostat dial on the front of the tank controls the target temperature. A.O. Smith heaters typically ship set to 120 degrees Fahrenheit, which is a safe default. You can turn the dial up or down to adjust, but do not exceed 140 degrees unless you have a specific reason—higher temperatures increase the risk of scalding and reduce the heater's lifespan.

If you have an electric heater, there is no visible flame, but you can feel the tank to check if it is warming. Place your hand on the side of the tank (not the top) after 15 minutes—it should feel warm to the touch. If it is still cold after 30 minutes, check that the breaker is fully in the On position and has not tripped.

Safety Reminders Before You Start

Before turning on your water heater, make sure the area around it is clear of clutter, flammable materials, and cardboard boxes. Gas heaters need at least 12 inches of clearance on all sides for proper air flow and to prevent accidental ignition of nearby items.

If you smell gas at any point during startup, do not attempt to light the pilot. Turn the control dial to Off when ready, leave the area, and call your gas company's emergency line from outside the home. A strong gas smell can mean a leak in the line or a failed valve, both of which require professional repair.

If you have recently moved into a home or the heater has been off for more than a few weeks, the pilot may take longer to light because air has filled the gas line. This is normal. Keep trying in 5-minute intervals up to three times. If it still will not light after three attempts, stop and contact a technician.

Frequently Asked Questions

How long should I hold the pilot button down?

Hold it down for 30 to 60 seconds after you see the pilot flame appear. This gives the thermocouple time to heat up and sense that the pilot is burning. Releasing too early can cause the pilot to go out once you let go of the button.

What if my water heater has a red reset button instead of a dial?

Some A.O. Smith models use a red reset button for the pilot instead of a dial. Press and hold the button while lighting the pilot, then release once the flame is stable. The process is the same—you are just using a button instead of a dial to control the gas flow.

Can I turn on the heater if the tank is empty?

Yes, you can turn on an empty tank, but do not run the heater for more than a few minutes without water in it. Turn it off and fill the tank before using it. Running a gas heater dry can damage the heating elements and create a safety hazard.

Why is my heater making a loud popping sound?

Popping or banging sounds usually mean sediment has built up inside the tank and is being heated. This is normal in areas with hard water. The sound is not dangerous, but flushing the tank once a year can reduce it. If the sound is very loud or accompanied by leaking, contact a technician.

Do I need to bleed air from the gas line before lighting?

No. A.O. Smith water heaters are designed to purge air automatically when you turn the dial to Pilot and hold it. You do not need to do anything special. Just follow the standard lighting steps and the air will escape as gas flows through.