AP917HD-S - Aqua-Pure Filtration System Replacement Cartridge - AP9043M AP917HD S Replacement Cartridge for AP904 Filtration System Whole House Water Filter The 3M Aqua Pure AP917HD S is the official replacement cartridge for the AP904 Whole House Filtration System. This high performance cartridge features advanced carbon block filtration combined with scale inhibition to help reduce sediment, chlorine taste and odor, and protect plumbing systems from scale buildup. Designed for easy maintenance, it uses a sanitary