20 Big Blue filter housing suitable for high-flow and heavy sediment applications. The opaque blue sump is made of reinforced polypropylene for strength and resistance to chemicals, and the black cap is made of high-flow polypropylene (HFPP) for stiffness. Water filters remove undesirable particles, chemicals, and microorganisms from water by means of a semipermeable barrier, adsorption, or biological processes. They are made of densely packed synthetic or natural fibers that trap suspended particles, materials that block microbes or adsorb unwanted chemicals,