To relight a Unitrol water heater, first find the gas regulator valve and turn it off. Allow five minutes to pass before removing the cover that shields the burner. Move the gas regulator to the pilot setting, and hold it in. Light the pilot light manually with a long lighter or match. Continue to press the gas regulator valve for one minute after the pilot light is lit, and then replace the burner cover.
If the pilot light is lit successfully, a muffled sound is heard upon the release of the gas regulator valve. This is the main burner igniting. Listen for that sound before replacing the burner cover. If it does not occur, or if the pilot light goes out after the gas regulator is released, repeat the lighting process. If it refuses to light after several tries, contact a professional or consider replacing the water heater.
Some water heater models do not require a lighter or a match. Instead, they use a built-in spark pilot igniter that is deployed with the press of a red or black button commonly labelled "ignition," and it is typically located on the side of the gas valve. Listen for a click; that is the igniter sparking. Additionally, in place of holding down the gas regulator, some models have a red button that starts the flow of gas to the pilot light. Deploy it in the same manner as the gas regulator.