An apparatus for automatically maintaining the water level of a body of water, such as a pool, is described herein. The present invention comprises a float body contained within a float housing chamber and selectively coupled to a float valve, a ball check valve employed as a means for isolating the pressurized water in the circulation system of a body of water from the water in the float chamber and, after pump operation has ceased, allowing the passage of supply water from the float chamber of the apparatus of the circulation system of a body of water. Flexible conduits or tubing may be provided for ease of installation. Furthermore, the present invention is intended to be conveniently located near the equipment of the circulation system for the body of water.