Where our water data comes from

KnowYourExposure is built entirely on official, public government data. We do not test water ourselves; we aggregate and make searchable the same federal and state datasets regulators use, so you can see what your utility has reported.

Our Data Sources

EPA UCMR5 (2023-2025): the EPA's Fifth Unregulated Contaminant Monitoring Rule, which tested public water systems nationwide for 29 PFAS compounds and lithium.

EPA SDWIS: the Safe Drinking Water Information System, covering regulated contaminant monitoring and violations for 120+ contaminants including arsenic, nitrate, radium, and disinfection byproducts.

EPA Lead and Copper Rule (LCR): utility-reported 90th-percentile lead and copper sampling results.

EPA ECHO: the Enforcement and Compliance History Online database of Safe Drinking Water Act violations and enforcement actions.

Geographic crosswalks linking ZIP codes to counties and public water systems, so a single address resolves to the utilities that serve it.

How We Handle the Data

We report utility-submitted values as recorded and cite the EPA program each figure comes from. Where a dataset is incomplete or a system has not reported recent results, we say so rather than filling gaps with estimates.