Water quality
What is in your tap water?
Enter a zip code for the contaminants your utility reported, each against a health guideline, and one score.
Cities with the most contaminants
Major US cities with the highest contaminant counts (EWG data, ranked September 28, 2026)
How we score
We count the contaminants reported above an EWG health guideline and weight each by the harm that guideline protects against (cancer 3, development and nervous system 2, others 1), on a curve where the first few exceedances move the score most. 8 and above is good, 5 and above is fair. A contaminant with no health guideline never counts against a city.
Where the data comes from
- Contaminant levels are utility averages compiled by the Environmental Working Group’s Tap Water Database from state and federal records; each report shows its test years.
- Health guidelines are EWG’s, set by federal or state public-health authorities; they are stricter than legal limits, which are also shown.
- What the Sans Water Purifier is tested to reduce comes from SGS, an ISO/IEC 17025 laboratory, and is shown with the lab’s own figure. Everything else is marked expected or not tested.