The first sign of trouble with your water heater's pilot light is usually a cold shower. Your heater's pilot light allows the burner to cycle on and off while maintaining the water in the tank at a constant temperature. When the pilot light goes out for any reason, the thermocouple closes the burner's gas supply valve to prevent gas escaping and filling your house. When your pilot will not light or does not remain lit, you might be able to save the price of a service call by taking a few minutes to troubleshoot the problem.
Remove the pilot light access cover. It is located near the bottom of the tank. If you smell gas, do not attempt to light the heater. If the smell does not dissipate, replace the heater's control valve before proceeding. The control valve is the box located by the access cover. It consists of the on/off/pilot dial as well as the thermostat dial. Consult manufacturer's documentation for replacement instructions on your model.
Turn the thermostat on the water heater to the lowest setting.
Turn the gas control valve to the "Pilot" position.
Inspect the burner area with a flashlight. Clean out any dust or debris before attempting to light the pilot.
Press the gas control valve down in the "Pilot" position, and hold the flame from your match or lighter underneath the pilot light.
If the pilot fails to ignite, check the gas supply to the heater. Make sure all supply valves are open.
If the gas supply is good, the pilot light's orifice or gas jet might be plugged. The orifice is the small tip attached to the pilot light's gas supply tube. Use a small wrench to remove it. Inspect the tip and remove any obstruction by tapping gently against a hard surface or blowing through it. Once you are satisfied that the orifice is clear, try lighting the pilot again and proceed to the next step. If it still does not light, replace the gas control valve.
Remove the flame from the pilot light as soon as it ignites. Continue to hold the gas control valve down for at least two minutes to allow the thermocouple to heat up. The thermocouple is the small metal rod located directly above the pilot light. It is designed to allow the burner to operate only when the pilot light is functioning.
Release the gas control valve. If the pilot light goes out, check the fittings between the thermocouple and the gas control valve. A loose fitting to the control valve can keep the thermocouple from operating properly. If the fittings are tight and the problem persists, replace the thermocouple.
Strong drafts can keep the pilot light from operating properly. Close the access panel when you have finished lighting the pilot.
Do not attempt to light the pilot if you smell gas. Do not turn the gas control valve into the operating position until you have closed the access panel.