HWD 48sqft Pro-Grid DE Filter Pro-Grid vertical grid D.E. filters provide superior water clarity, efficient flow and large cleaning capacity for pools and spas of all types and sizes. Constructed with high-strength reinforced thermoplastic, Pro-Grid combines high-technology features and "service-ease" design for an unparalleled filtration value for both new pool and aftermarket installations. In addition, Pro-Grid delivers low maintenance and dependable operation. Features Reinforced thermoplastic filter tanks constructed from durable glass reinforced copolymer to meet the demands of the toughest applications and environmental conditions, including in-floor cleaning systems Self-Aligned tank top and bottom make access to servicing the grid elements fast and simple Heavy-duty, tamper-proof one-piece flange clamp securely fastens tank top and bottom, allowing for quick access to all internal components without disturbing piping or connections High impact grid elements designed for up-flow filtration and top-down backwashing for maximum efficiency Integral lift handles and uniform low-profile base make removal of grid nest fast and simple Inlet diffuser elbow distributes flow of unfiltered water evenly to all filter elements and provides even distribution of D.E. to grids 72 ft filter made of reinforced thermoplastic allows for both commercial and large residential applications and years of non-corrosive, trouble-free performance New High capacity, rapid release manual air relief valve bleeds air with a quick quarter turn of the lever