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, warranty and price. The Express Water Anti-Scale WH300SCPS wins on flow and running cost. The 3M Aqua-Pure AP903 costs $80.13 less ($422.99 vs $503.12).
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 Anti-Scale WH300SCPS
#16 in CartridgeFull review
For hard city water where scale on the water heater is the main worry but a softener is too much. It doesn’t soften.
Amazon $503.12$503.12
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), warranty (25-year warranty vs 1-year warranty) and price ($422.99 vs $503.12).
- Choose the Express Water Anti-Scale WH300SCPS for flow (15 gpm service flow vs 10 gpm service flow) and running cost ($1.84 per 1,000 gallons ($183.67 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 Anti-Scale WH300SCPS |
|---|---|---|
| Overall rating | 3.1/5 | 2.4/5 |
| Running cost 25% | 8 $2.45 per 1,000 gallons ($244.77 every 100,000 gallons) | 18 $1.84 per 1,000 gallons ($183.67 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 | 28 $503.12 |
| Warranty 15% | 100 25-year warranty | 0 1-year warranty |
Specifications
| 3M Aqua-Pure AP903 | Express Water Anti-Scale WH300SCPS | |
|---|---|---|
| Filtration | ||
| Capacity | 100,000 gallons | 100,000 gallons |
| Replacement filters or media | $244.77 | $183.67 |
| Running cost | $2.45 per 1,000 gal | $1.84 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 |