A heating tank assembly for a hot water dispenser having a tank body, an electric heating element, a magnetic switch, and a movable float. The tank body has a plurality of walls and a main heating chamber for storing and heating water. At least a portion of the electric heating element is located within the main heating chamber of the tank body. The magnetic switch is electrically connected to the heating element and acts as a protective switch to the heating element. The movable float is located within the tank body and has a magnet that closes the magnetic switch when sufficient water is present in the tank. The heating tank assembly may also include at least one thermal cutout device. The thermal cutout device acts as a backup and will shut off the heating element if the heating element reaches a preset maximum temperature. The present invention also includes a method for determining whether a heating tank assembly of a hot water dispenser has little or no water by including a step of moving the float to or from the magnetic switch and closing the magnetic switch when sufficient water is present in the tank body. The present invention also includes a method for manufacturing a heating tank assembly of a hot water dispenser.