Abstract: The apparatus of this invention consists of a float assembly, constrained in its vertical movement by a perforated riser. The riser is surrounded by a flexible, bellows conduit which will allow the float assembly to move up and down the vertically disposed riser. The float assembly supports a weir collar designed to allow multiple weir orifice openings of different sizes. The flexible, bellows conduit is watertight, and prevents water from entering the riser below the float assembly that is buoyed just below the surface of the liquid basin. The riser is connected to an outlet that discharges the liquid from the liquid basin.