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How does a gas hot water heater thermostat work?


If you have a gas water heater and the pilot light will not stay lit, it’s most likely due to a failed thermocouple that will need to be replaced.  Thermocouple failure is a common problem with residential gas water heaters.

The thermocouple is a thermoelectric device that shuts off the gas supply to the water heater if the pilot light goes out.  Its function is simple but very important for safety.  The thermocouple generates a small amount of electrical current when it has been heated by the flame.  This small amount of electric current keeps the pilot gas valve open.  If the pilot light goes out, the electrical current stops and the gas valve closes.  Simply put; no flame, no gas flow.

Not all gas water heaters have a thermocouple. Some newer models have an advanced temperature control system. Essentially, it is a microprocessor that constantly monitors and controls burner operation and maintains consistent and accurate water temperature levels. The flashing LED indicates that the pilot is on.

If you have a gas water heater with a thermocouple failure, and the water heater is under warranty, you can contact the manufacturer of the water heater and request a free replacement part. It is important to have the model number and serial number available when you contact the manufacturer.

Unfortunately, you will most likely have to wait for shipment of the thermocouple, which may take several days. If you are like most people and you do not want to live without hot water for several days, you may decide to replace the part without going through the warranty claim process. Instead, you may opt to purchase a universal thermocouple rather than wait for the manufacturer’s part to arrive. However it is important to note that it is most likely that the universal thermocouple is not covered by the manufacturer’s warranty and this is an expense you would need to pay for should you opt not to wait for shipment. Universal thermocouples are commonly stocked for most models. It is important to verify that your model of water heater can utilize a universal thermocouple.