It holds particles smaller than 45 microns in the pool water. It ensures that small impurities are kept in the filter. It cleans and clarifies the pool water. It is used to remove small particles in pool water by clumping. High capacity filtering is provided in pools where sand filters are used. However, these filters cannot hold impurities smaller than 45 microns, and these particles easily pass through the filter bed and are found in the pool water. These small particles are held by the Polyaluminum chloride (PAC) molecule and kept in the filter, thus eliminating the pollution in the pool water.