Review on 3M Aqua-Pure AP917HD-S Replacement Water Filter: Enhanced Sanitary Quick 💧 Change for AP904 System, Reduces Sediment, Chlorine Taste, Odor, and Scale by Lisa Barber

The 3M AP904 Whole House Filter works as described but the Watts WH-LD pre-filter which must be purchased should be from Culligan WH-HD200. -C Heavy duty whole house filtration system with 1" inlet/outlet. This should be used as it has a 1" NPT threaded inlet and outlet just like the 3M AP904 Whole House Filter. The Watts WH-LD has a 3/4" NPT inlet and outlet which means when used as a pre-filter it will restrict flow to the AP904. This is why I returned the Watts WH-LD filter, I didn't read the specs on Watts as I figured if they said it was bought with a 3M AP904 it must be correct.