Abstract: A vessel for containing liquid includes a floor perimetrically surrounded by a plurality of upwardly projecting walls; at least one exit port incorporated into at least one of the walls proximate to an upper edge of the at least one wall; and a liquid circulation pump apparatus. The liquid circulation pump apparatus includes a first conduit in fluid communication with the vessel; a circulation pump positioned downstream from and in fluid communication with the first conduit; a supply conduit positioned downstream from and in fluid communication with the circulation pump; and a diverter valve positioned downstream of the circulation pump and upstream of the supply conduit. The circulation pump is adapted to pump liquid from the vessel through the first conduit and deliver liquid through the supply conduit to the exit port. The diverter valve is adapted to change a rate of flow of liquid supplied to the exit port.