Tools that do the arithmetic.
Each one works from public records and makers’ own figures, and shows its working. Nothing to sign up for.
ZIP code lookup
Your utility’s results from EPA’s records, the worst first, with the certification claim that handles each.
Five-year cost calculator
Filters side by side over five years: the system, every cartridge at the maker’s gallon or month rating, and the cost per gallon for your household.
Water softener cost, salt included
Every softener’s five years at your water’s hardness: salt at the setting the maker or a listing stands behind, how often it regenerates, and the system.
Refrigerator filter finder
Your fridge’s model number, or its filter’s, to the filter that fits, what its listing covers, and certified copies that cost less.
Certified lab finder
The labs your state certifies to test drinking water, from the state’s own list, for a well or a check on your tap.
Where to go next
- How the numbers are worked outWhere every figure comes from, and what each tool assumes.Read the methodology
- NSF/ANSI standards, decodedWhat each number on a filter box covers, and what it does not.Every standard
- GuidesEach one opens with the answer, and every source is listed with the date it was checked.Read the guides