HWD 24in Pro Series Sand Filter w/ Valve Pro Series high-rate sand filters are the very latest in pool filter technology. Molded of durable, corrosion-proof reinforced thermoplastic, Pro Series filters feature an advanced, self-cleaning lateral under drain system for smooth, efficient flow and totally balanced backwashing. Pro Series sand filters also feature a self-cleaning 360-degree slotted lateral for totally balanced flow and backwashing. Their integral top diffuser ensures even distribution of water over the top of sand media bed with full size internal piping for smooth, free-flowing performance. So for crystal clear water with only minimal care, pool professionals choose Pro Series. Features Top diffuser ensures even distribution of water over the top of the sand media bed. All internal piping is 2" to give smooth, free-flowing performance Manual air relief purges any trapped air during operation of the filter system Unitized, corrosion-proof, filter tank molded of rugged, colorfast reinforced thermoplastic dependable, all weather performance 7-position Hayward Vari-Flo™ control valve with easy-to-use lever-action handle lets you dial any of the 7-valve/filter functions. Integral sight glass lets you see when backwash cycle is completed Precision-engineered umbrella-fold self cleaning laterals for balanced flow and backwashing, plus easy serviceability Large pressure sand/water drain for rapid winterizing or servicing