3M Aqua-Pure AP903
#4 in CartridgeFull review
A certified, low mess choice for city water with chlorine, for owners who would rather pay more per cartridge than handle filters.
Amazon $422.99$422.99
The 3M Aqua-Pure AP903 is the better whole-house water filter overall, rated 3.1 to 2.4. The 3M Aqua-Pure AP903 leads on certification and warranty. The Express Water Ultimate Protection WH300SCKP wins on flow and running cost. The 3M Aqua-Pure AP903 costs $20.15 less ($422.99 vs $443.14).
Prices were last checked November 9, 2026. Product prices and availability are accurate as of that date and are subject to change; the price and availability shown on Amazon or the retailer's site at the time of purchase apply. As an Amazon Associate we earn from qualifying purchases.
Express Water Ultimate Protection WH300SCKP
#15 in CartridgeFull review
The best value of Express Water’s three stage systems, for hard city water with old pipes. Its claims aren’t certified.
Amazon $443.14$443.14
Which should you buy?
- Choose the 3M Aqua-Pure AP903 for certification (certified to NSF/ANSI 42 vs no certification in a public listing, no tested to claim) and warranty (25-year warranty vs 1-year warranty).
- Choose the Express Water Ultimate Protection WH300SCKP for flow (15 gpm service flow vs 10 gpm service flow) and running cost ($1.78 per 1,000 gallons ($177.64 every 100,000 gallons) vs $2.45 per 1,000 gallons ($244.77 every 100,000 gallons)).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every cartridge whole-house water filter; a clear win is highlighted. How we rank explains each one.
| Factor weight | 3M Aqua-Pure AP903 | Express Water Ultimate Protection WH300SCKP |
|---|---|---|
| Overall rating | 3.1/5 | 2.4/5 |
| Running cost 25% | 8 $2.45 per 1,000 gallons ($244.77 every 100,000 gallons) | 19 $1.78 per 1,000 gallons ($177.64 every 100,000 gallons) |
| Certification 25% | 60 certified to NSF/ANSI 42 | 0 no certification in a public listing, no tested to claim |
| Flow 15% | 50 10 gpm service flow | 100 15 gpm service flow |
| Price 20% | 38 $422.99 | 35 $443.14 |
| Warranty 15% | 100 25-year warranty | 0 1-year warranty |
Specifications
| 3M Aqua-Pure AP903 | Express Water Ultimate Protection WH300SCKP | |
|---|---|---|
| Filtration | ||
| Capacity | 100,000 gallons | 100,000 gallons |
| Replacement filters or media | $244.77 | $177.64 |
| Running cost | $2.45 per 1,000 gal | $1.78 per 1,000 gal |
| Stages | 1 | 3 |
| Certified | NSF/ANSI 42 | - |
| Chloramine | No | No |
| PFAS | No | No |
| Build | ||
| Flow | 10 gpm | 15 gpm |
| Ports | 1 in | 1 in |
| UV stage | No | No |
| Warranty | 25 years | 1 year |