If the pilot light pilot light on your gas water heater will not stay lit or the burner that will not ignite, you likely have a defective thermocouple. A thermocouple works by sensing the heat from the pilot flame and, when the temperature is high enough, it sends a signal to the gas valve to supply gas to the pilot light.
A thermocouple is an important safety device that prevents gas from being sent to the pilot and burner if there is no source of ignition. If the gas were to continue flowing to an unlit pilot light, the result would be a hazardous buildup of natural gas. While the part sends an electric signal to the gas valve, it doesn't use any electricity itself, but instead uses heat to generate an electrical impulse.
The first sign that a thermocouple is failing is that the supply of hot water is reduced or stopped altogether as the thermocouple receives false signals and shuts off the gas, thinking the pilot light is out. If the pilot light remains lit but the gas supply is shut off, the thermocouple is the likely culprit. A plumber should inspect the unit to diagnose the problem. If the thermocouple has stopped working, it is not repairable and should be replaced.
Have questions about your water heater? Call Grand Lake Plumbing, we can help with all your plumbing and hot water needs.