Turn a hot water faucet on inside your home. Open the water supply valve by turning the valve counter-clockwise.
Turn the hot water faucet off inside your home once you establish a steady stream of water. A steady water stream indicates a full tank.
Flip the water heater breaker on inside the breaker panel to turn an electric water heater on.
Turn the temperature control valve to the lowest temperature setting on a gas water heater. Rotate the pilot control knob to the "Pilot" position. Both the valve and the knob are located on the gas control valve on the side of the water heater.
Remove the access panels from the bottom of the water heater to access the pilot inside the combustion chamber.
Push the pilot button down while lighting the pilot inside the combustion chamber. Locate the pilot button next to the pilot control knob. Hold the pilot button down for 20 or 30 seconds and slowly release it. If the pilot fails to remain lit, hold the button down once again and relight the pilot. You may need to repeat this several times to bleed the air from the gas line.
Replace the access panels onto the bottom of the water heater to cover the combustion chamber. Turn the pilot control knob to the "On" position and turn the temperature control valve to your desired water temperature.