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
The iSpring WGB21B is the better whole-house water filter overall, rated 3.4 to 2.0. The iSpring WGB21B leads on flow, running cost and certification. The iSpring WGB21B costs $102.01 less ($155.99 vs $258).
Pentair Pentek FloPlus Protect 20BB
#13 in CartridgeFull review
For a smaller home where PFAS in the water is the main worry. Its low flow rating suits one or two bathrooms.
Amazon $258$258
Prices were last checked November 2, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the iSpring WGB21B for flow (15 gpm service flow vs 5 gpm service flow), running cost ($0.90 per 1,000 gallons ($45.11 every 50,000 gallons) vs $4.69 per 1,000 gallons ($187.46 every 40,000 gallons)) and certification (tested to NSF/ANSI 42, not certified vs no certification in a public listing, no tested to claim).
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 | iSpring WGB21B | Pentair Pentek FloPlus Protect 20BB |
|---|---|---|
| Overall rating | 3.4/5 | 2.0/5 |
| Running cost 25% | 44 $0.90 per 1,000 gallons ($45.11 every 50,000 gallons) | 0 $4.69 per 1,000 gallons ($187.46 every 40,000 gallons) |
| Certification 25% | 30 tested to NSF/ANSI 42, not certified | 0 no certification in a public listing, no tested to claim |
| Flow 15% | 100 15 gpm service flow | 0 5 gpm service flow |
| Price 20% | 98 $155.99 | 68 $258 |
| Warranty 15% | 0 1-year warranty | 0 warranty not published, scored as none |
Specifications
| iSpring WGB21B | Pentair Pentek FloPlus Protect 20BB | |
|---|---|---|
| Filtration | ||
| Capacity | 50,000 gallons | 40,000 gallons |
| Replacement filters or media | $45.11 | $187.46 |
| Running cost | $0.90 per 1,000 gal | $4.69 per 1,000 gal |
| Stages | 2 | 1 |
| Tested to (not certified) | NSF/ANSI 42 | - |
| Chloramine | No | No |
| PFAS | No | Yes |
| Build | ||
| Flow | 15 gpm | 5 gpm |
| Ports | 1 in | 1 in |
| UV stage | No | No |
| Warranty | 1 year | - |