A hot water heater having a heating tank and a superjacent basin for receiving cold water to be delivered to the tank. A duct is provided leading from the basin into the tank for transferring water from the basin to the tank. A heater is provided for heating the water in the tank. Structure is provided in the duct for breaking up lime which may form at the upper level of the water in the tank and cut as a result of a continued heating of the water therein. The lime breakup structure includes a float and a retaining cage for controlling the movement of the float during delivery of cold water from the basin through the duct to the tank. The cage and float are removably carried in the hot water heater for facilitated installation and maintenance.