Tip & How-To about Water Heaters
If you are having trouble with the temperatures of your gas hot water heater fluctuating too much, or after changing the thermocouple of your gas hot water heater then you may need to change the complete gas valve and thermostat assembly. Also if you have changed the thermocouple and the pilot still will not stay lit, then the gas valve could be bad or the ECO (Emergency Cutout) may have activated and is open. This is a onetime device and cannot be replaced.
These instructions are for the older style gas valve and thermostat combination. These commonly have a large red knob that adjusts the temperature of the water. Also note that the burner tube nut for natural gas is right hand thread, but if you have LP or propane gas the burner tube nut is left hand thread.
The newer gas valve thermostat combinations that have come out recently are similar, but they have a well in the tank that the sensor slides into. The assembly is held fast with a set screw. With this type of gas valve and thermostat unit the tank does not need to be drained, but most of the rest of the change out is similar.
To change a gas hot water heater thermostat you will need to first buy a new gas valve for your hot water heater. The gas valve and the thermostat are integrated into one unit.
To replace the thermostat on a gas hot water heater you must follow these procedures....
1. Turn off the incoming water and drain the hot water heater.
2. Remove the pilot tube, the burner gas tube and the thermocouple from the gas valve. Turn off the gas line and remove from the gas valve.
3. Get a pump pliers or a wrench in behind the gas valve and turn the whole assembly CCW to remove it from the tank.
4. After applying pipe dope or tape to the new gas valve threads, turn the new gas valve into the tank by turning in a CW direction. Be careful not to damage the small wires to the ECO. They are the little red wires on the back. If you break them the assembly is irreparably damaged.
5. Reinstall the gas line, thermocouple, burner tube, and the pilot tube to the gas valve.
6. Fill tank with water. Make sure to open a hot water faucet and purge all air from the tank.
7. Check for leaks where the gas line hooks up with soapy water.
8. Relight pilot light and check operation.
9. Set the new temperature setting to a medium setting and then adjust the temperature to your liking from there and adequate time for heating completely
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