Data sources

Where our water-system information comes from, and how fresh it is.

Primary sources

• EPA public water system records and service-area data
• Utility Consumer Confidence Reports (CCRs), linked directly on each report
• State drinking-water program publications
• NSF and WQA certified-product listings for treatment claims

Provenance on every data point

Each value we show carries its source organization, reporting period, retrieval date and a confidence label. Modeled service boundaries are always labeled as “likely,” never as certain. If a current source-backed value is missing, we say it's missing rather than substituting a regional average.