The Raypak® Protégé™ 14" Above Ground Sand Filter is designed to last for years of use when maintained properly. Its purpose is to extract suspended particles (dirt) from the pool water, thereby keeping the water clear. A special filter sand is used to trap and collect the particles. The filtering action occurs as the water flows through the unit and the particles are trapped in the sand bed which forms the filter. Water enters through a valve on the top of the filter and then passes evenly though the filter. The filtered water then flows through the bottom side of the filter, up through the stand pipe, through a valve on the top, and then back into the pool though piping or hoses.