Filters Fast - 3M Aqua-Pure AP917HD-S Whole House Water Filter Cartridge

The AP917HD-S is the only consumable the 3M Aqua-Pure AP904 whole house system takes. Filters Fast sells it at $311.95 against a $349.99 list, drops the price to $301.95 each on 6 or more, and takes a further 5% off with free shipping on subscription orders, which fits a filter you replace on a fixed annual clock.

Inside is activated carbon plus 5 micron particulate filtration rated for 100,000 gallons, roughly 12 months of normal household use, at flow rates up to 20 gpm. The Sanitary Quick Change design threads on and off in minutes with no filter wrench and no handling of spent media. It carries independent certification for chlorine taste and odor and particulate reduction, feeds the scale inhibition that protects water heaters and fixtures, and averages 4.9 of 5 across 16 reviews on the Filters Fast page.

Where it gives ground: it fits nothing but the AP904-series head, so there is no cross-shopping to a cheaper compatible cartridge. And at roughly $300 a year it costs more annually than many under-sink filters cost outright. That is the price of running one cartridge for the whole house instead of several point-of-use filters on separate schedules.