Interactive tool

Compare County Water Quality

Put any two U.S. counties side by side on drinking-water violations, PFAS detection, and system coverage, straight from EPA SDWIS and UCMR5 testing.

Compiled by PlainWater

3,254
Counties available: 63
States & territories: 142,471
Water systems covered

According to the EPA's Safe Drinking Water Information System (SDWIS) and UCMR5 testing program, every figure in this comparison is pulled directly from official public water-system records. See our methodology for how violations and PFAS detections are counted.

Choose Counties to Compare

County A

County B

Need state-level aggregates? Use the state compare tool.

Popular comparisons

Los Angeles vs Richmond CA · NY → Harris vs Cook TX · IL → Maricopa vs San Diego AZ · CA → Suffolk vs Miami-Dade MA · FL →

Counties with the most violations

1Orange NY 85,938 violations 2Harris TX 78,495 violations 3Monroe PA 72,365 violations 4Bucks PA 59,577 violations 5Berks PA 54,767 violations 6Lubbock TX 50,449 violations

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Or pick any two counties above to build your own side-by-side comparison.

3,254 counties · 63 states available

Download the SDWIS/UCMR5 state landscape snapshot cited on this page: sdwis-state-landscape.csv (same CSV as /statistics, CC0).

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This page draws directly on EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.