A water heater gas valve works by opening and closing to control the intake of gas, regulating the temperature in the water tank. The gas valve is controlled by a thermostat, which signals for the valve to open with low temperatures and close when it reaches the heating threshold.
The gas valve on a water heater contains an electromagnet, which activates when heat from the pilot flame reaches the thermopile circuit. The activated electromagnet keeps the gas valve open, letting the gas flow into the main burner and pilot. When the pilot flame is out, the electromagnet deactivates, and the gas supply closes.
Water heater gas valves have a thermostat with a probe that inserts directly into the water tank for the most precise reading. The probe on the back side of the gas valve includes an energy cut-off switch, which disables the water heater if the water temperature reaches 190 degrees Fahrenheit. Standard water heaters have a knob located on the front of the gas valve where the owner can adjust the temperature.
The water in a water heater is constantly being heated to maintain its temperature, which leads to standby heat losses and wasted energy. Standby heat loss can be avoided or minimized with the use of heavily insulated, tankless and demand water heaters.