Whole House Dual Water Filtration Systems - 20" X 4.5" 20" Big Blue Whole House water filtration systems - Excellent to remove Chlorine, Odors and many other chemicals and contaminants. Effectively eliminates many impurities from tap water to offer sparkling clean and great tasting water throughout your whole house. Complete Systems with Filter Cartridge, Wall Bracket and Housing Wrench. Standard size filter 4.5”x 20” this can replace 3M™ Aqua-Pure™ Whole of house filter system, AP802