Waterco 22207188 18" Side Mount HRV Commercial Sand Filter is one of the most common types of pool filters. Pool water free from debris and other contaminants is important for maintaining swimmers’ health and safety, not to mention happiness. Manufactured with high grade fiberglass and resins for durability, this sand/media filter will give you years of clean pool water. Depending on the choice of media, this medium filters out everything larger than 3 - 40 microns.