A combustion chamber is disposed below the water container of a water heater and formed at least partially by a shell. A burner disposed within the combustion chamber and a fuel supply line is connected to the burner. A valve associated with the fuel supply line. A combustion chamber sensor is disposed within the combustion chamber and adapted to sense a rise in temperature indicative of an abnormality in the combustion chamber. A circuit connected to the sensor and the valve such that the circuit triggers the valve to shut off fuel to the burner in response to a sensed temperature by the sensor.
