If you have shut off your water heater for draining or repairs or to conserve fuel while away on a trip, you must relight the pilot manually. Here are a few steps to help you relight your water heater safely.
Set the gas-control knob to the Off position and turn the thermostat to its lowest setting (typically clockwise in both cases). Wait 5 minutes for any gas to clear. If after 5 minutes you smell gas, do not proceed. Call the utility company for immediate service.
Open or remove the outer and inner access covers for the burning chamber using a wrench or pliers. Use a flashlight to locate the end of the pilot-light tube that extends from the gas-control valve into the burning chamber. Adjust your position so you can comfortably reach this point with a wooden match and see what you are doing.
Turn the control knob to the pilot position and immediately hold a match near the end of the pilot-light tube. Depress and hold the reset button on the gas-control valve (see illustration). Remove the match as soon as the pilot lights, but keep the button depressed for about a minute.
If the pilot does not remain lighted, repeat all these steps. Otherwise, turn the gas cock on the control valve to the On position, set the thermostat to the desired temperature and replace the access panels.