iSpring WGB21B
#2 in CartridgeFull review
A low cost first whole-house filter for city water with chlorine taste. Expect to change filters several times a year.
Amazon $155.99$155.99
3.1/5
A certified, low mess choice for city water with chlorine, for owners who would rather pay more per cartridge than handle filters.
- $2.45 per 1,000 galRunning cost
- 100,000 gallonsCapacity
- 10 gpmFlow
- NSF/ANSI 42Certified
Check price at Amazon$422.99
Price checked November 2, 2026. As an Amazon Associate we earn from qualifying purchases.
Pros
- NSF certified for chlorine taste and odor, which few whole-house filters are
- One sanitary cartridge swaps without touching filter media or a wet housing
- A year between changes in most homes
Cons
- A single cartridge costs $244.77, so running cost is high
- Rated service flow of 10 gpm is lower than the big housing systems
- Not built for chloramine
The 3M Aqua-Pure AP900 Series family
Every 3M Aqua-Pure AP900 Series model we rank, smallest first. Ratings compare each against its own build.
| Model | Running cost | Rating | Price |
|---|---|---|---|
| 3M Aqua-Pure AP903 (this one) | $2.45 per 1,000 gal | 3.1/5 | $422.99 |
| 3M Aqua-Pure AP904 | $3.47 per 1,000 gal | 3.1/5 | $421.18 |
How it scores
The rating comes from 5 measured or published factors, each scored 0-100 against fixed reference points for its build. How we rank explains each one.
Specifications
| Model number | AP903 |
|---|---|
| Filtration | |
| Capacity | 100,000 gallons |
| Replacement filters or media | $244.77 |
| Running cost | $2.45 per 1,000 gal |
| Stages | 1 |
| Certified | NSF/ANSI 42 |
| Chloramine | No |
| PFAS | No |
| Build | |
| Flow | 10 gpm |
| Ports | 1 in |
| UV stage | No |
| Warranty | 25 years |
Alternatives in this build
Waterdrop WHF3T-PG
#3 in CartridgeFull review
A lower priced three stage big blue system for city water. Running cost is hard to judge without a gallon rating.
Amazon $269.99$269.99
iSpring WGB22B
#5 in CartridgeFull review
A sensible upgrade on the WGB21B for a family on chlorinated city water, with filters that last longer and cost little per gallon.
Amazon $286.70$286.70
Compare
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