AO Smith water heaters are widely used in many homes across the United States. Whether dealing with a gas-fired model that uses a pilot light or an electric unit that relies on a reliable electrical supply, getting a water heater back online involves a few careful steps. This guide explains how to turn on an AO Smith water heater, cover safety considerations, and offer troubleshooting tips to help homeowners restore hot water quickly and safely.

Understanding Your AO Smith Water Heater

AO Smith manufactures several types of residential water heaters, including gas and electric models. The basic goal is simple: deliver hot water on demand while maintaining efficiency and safety. Gas models typically use a thermostat and a pilot light or electronic ignition, whereas electric models rely on heating elements controlled by a thermostat and protected by a high-temperature limit switch. Knowing which type you own—and its key components—helps in planning the startup process and recognizing when professional help is needed.

Safety First

Before attempting any startup or inspection, observe these safety guidelines. Turn off power or gas supply if advised by the manufacturer or if there is any sign of damage. Do not attempt to light a pilot or reset components if the area is damp, flooded, or crowded with flammable materials. For gas models, ensure the home area is well-ventilated and that the flue is unobstructed. For electric models, confirm the circuit breaker is appropriate for the water heater’s amperage and that the wiring is intact. If you smell gas strongly, leave the area and contact the utility company or emergency services.

Gas Water Heaters: Turning On The Pilot And Heater

Gas AO Smith models may use a standing pilot or electronic ignition. The process below covers a standing-pilot system, which is common in older installations. If the unit uses electronic ignition, follow the manufacturer’s instructions specific to that model in the user manual.

Check the Gas Supply: Ensure the gas shutoff valve is fully open. If you smell gas, do not proceed; evacuate and call the gas provider.
Access the Thermostat Area: Locate the front panel and remove the screws to access the thermostat and pilot assembly.
Inspect the Pilot Light: If the pilot is out, hold the reset or pilot button (per model instruction) and light the pilot using the built-in igniter or a long lighter if required. Maintain the button for 30–60 seconds to allow the thermocouple to heat up.
Relight Procedure: If the pilot relights, replace the access panel and turn the gas control knob to the “ON” or “Hot Water” position. Some AO Smith models require turning to a specific setting like “PILOT” before lighting, then back to “ON.”
Set the Temperature: Use the thermostat dial to set the desired water temperature, typically around 120°F for most households. Avoid very high temperatures to reduce scald risk and energy use.
Test the Water: After the panel is secured, run hot water from a faucet to confirm the heater is producing heat within a reasonable time frame. If there is no heat after a reasonable delay (10–20 minutes), stop and re-check the gas supply, ignition, and thermostat.

Important note: If the pilot repeatedly goes out or the unit fails to light, there may be a faulty thermocouple, dirty burner, or gas pressure issue. In such cases, contact a licensed gas technician to diagnose and repair the system.

Electric Water Heaters: Restoring Power And Resetting

Electric AO Smith models rely on networked electrical components, and safety procedures differ from gas units. Follow these steps to turn on and verify proper operation:

Power Check: Ensure the water heater is plugged into a live circuit and that the wall breaker or fuse is intact. If the breaker has tripped, reset it and test the water heater after a few minutes.
Thermostat Verification: Locate the upper and lower thermostats and verify they are set to a safe temperature, typically around 120°F. If the thermostat readings seem erratic or unresponsive, the thermostat may need replacement or calibration.
Reset the System: Many electric AO Smith units include a reset button on the upper thermostat. Press and hold the reset button for several seconds to restart the system after a detected fault. If the reset repeatedly trips, there could be a heating element issue or a thermostat fault.
Inspect Heating Elements: If heat is intermittent or absent, a failed heating element could be the cause. This typically requires a service call to replace the element(s). Do not attempt element replacement if unsure about electrical work.
Flush and Check: Regularly flushing sediment from an electric water heater helps maintain efficiency. If the tank is heavily mineralized, performance may wane even after power restoration.

Common Issues And Quick Fixes

Understanding typical problems can speed up troubleshooting. The following quick checks help determine whether the issue is simple or requires professional service.

No hot water (gas): Confirm gas supply, pilot status, and thermostat setting. Check for a stubborn pilot or gas shutoff valve issues.
No hot water (electric): Check the circuit breaker and reset button. Inspect the upper thermostat if the reset function is not resolving the issue.
<strongLow hot water temperatures: Increase thermostat to recommended settings and check for sediment buildup. Consider flushing the tank and inspecting the dip tube if temperatures remain low.
<strongInconsistent water temperature: This can indicate a faulty thermostat, heating element, or a cross-connection in hot and cold lines. A professional assessment may be needed.
<strongStrange noises or leaks: Sediment buildup can cause popping sounds and reduce efficiency. Leaks near the tank edges require immediate attention to prevent water damage.

Maintenance Tips To Prevent Future Problems

Proactive maintenance extends the life of AO Smith water heaters and minimizes startup issues. Consider the following best practices.

Schedule annual inspections: A professional can verify gas pressures, venting, and electrical connections, reducing the chance of future failures.
Flush the tank yearly: Sediment can insulate heating elements and reduce efficiency. Regular flushing helps maintain performance and extends tank life.
Test the pressure relief valve: Lift the discharge lever and let water flow into a nearby drain. If it does not release water, the valve may need replacement.
Inspect the anode rod: A corroded anode rod shortens tank life. Replace as recommended by the manufacturer to protect the interior lining.
Replace aging components: Thermostats, heating elements, and igniters have finite lifespans. Proactive replacement reduces unexpected outages.

For homeowners seeking a detailed, model-specific guide, consult the AO Smith user manual corresponding to the exact model number. Model variations may include different ignition methods, thermostat configurations, and reset procedures. When in doubt, contact a licensed technician for safe assessment and service.