Hot Water Heater Trouble Shooting

[jmowreader]

6. Sounds like a mercury sensor problem to me

Your water heater has three sensors on it: a flammable vapor sensor, a thermocouple and a mercury sensor.

The flammable vapor sensor detects flammable quantities of flammable vapor and shuts off the gas so the water heater won't burn your house down.

The thermocouple watches the pilot light, and if that goes out the thermocouple shuts off the gas to help prevent the house from burning down.

The mercury sensor is a sealed glass tube with mercury in it that sits in the water in the tank and monitors the water temperature. It controls the flow of gas to the burner.

These fail in two ways - they can fail so that the gas will never go on, or that it never goes off. These are not hard to change, but since you've got a tank of overheated water on your hands I'd recommend calling a plumber to change it - they are trained to deal with this.