PlainWater

Our Methodology

Data Sources

PlainWater draws from two authoritative Environmental Protection Agency datasets to provide comprehensive drinking water quality information:

  • EPA SDWIS (Safe Drinking Water Information System): Quarterly bulk data from EPA's ECHO program covering all public water systems, their violation histories, and system characteristics. The SDWIS is the primary federal database for Safe Drinking Water Act compliance.
  • EPA UCMR5 (Fifth Unregulated Contaminant Monitoring Rule): PFAS "forever chemical" testing data from 2023–2025. UCMR5 required public water systems serving 3,300+ people to test for 29 PFAS compounds and other contaminants not yet regulated under the Safe Drinking Water Act.

Processing Pipeline

We download quarterly SDWIS bulk data exports from EPA's ECHO program and merge them with UCMR5 PFAS testing results. Processing steps:

  • System profiles: Each water system's basic characteristics (type, ownership, population served, source water type) are extracted from SDWIS.
  • Violation records: All violations are classified as health-based (Maximum Contaminant Level violations, Treatment Technique violations) or monitoring/reporting violations. Health-based violations are highlighted as the higher-severity category.
  • PFAS results: UCMR5 results are merged by water system PWSID, showing each detected PFAS compound with its measured concentration and EPA health advisory level comparison.
  • Geographic aggregation: County and state views aggregate system-level data to show regional compliance patterns.
  • Contaminant profiles: Cross-system analysis shows which contaminants have been detected most widely.

Violation Classification

Violations recorded in the SDWIS database fall into two main categories, each indicating different types of compliance concerns:

  • Health-Based Violations: Maximum Contaminant Level (MCL) exceedances, Treatment Technique (TT) violations, and Surface Water Treatment Rule violations. These directly affect water safety.
  • Monitoring & Reporting (M&R) Violations: Failures to test on schedule or report results as required. These do not necessarily indicate contamination but show gaps in compliance tracking.

Limitations

  • Data reflects EPA's SDWIS and is subject to reporting delays, violations may appear weeks to months after they occur.
  • UCMR5 PFAS testing only applies to systems serving 3,300+ people; smaller systems are not included in UCMR5 data.
  • Violation records show historical compliance issues; resolved violations from years ago remain in the historical record.
  • Private wells and very small community water systems may have incomplete or no data.

Data Collection Method

EPA SDWIS data is compiled from state drinking water programs. Under the Safe Drinking Water Act, each state has primary enforcement responsibility (primacy) for its public water systems and reports compliance data to EPA. States collect water quality test results, violation notices, and system characteristics from water utilities, then submit this data to EPA through the SDWIS database. UCMR5 data is collected directly from water systems under EPA authority, systems above the population threshold are required to test and report results to EPA. We download both datasets in bulk and merge them by water system identifier (PWSID) to create unified profiles.

Update Schedule

EPA publishes SDWIS bulk data updates quarterly through the ECHO program. UCMR5 results are published on a rolling basis as testing is completed (2023–2025 testing cycle). We refresh our database when new quarterly SDWIS exports and UCMR5 results become available. Between updates, new violations and test results may not be reflected.

Not Affiliated

PlainWater is not affiliated with the Environmental Protection Agency or any federal, state, or local government agency. Data is provided for informational purposes only. Always consult your local water utility's Consumer Confidence Report (CCR) for the most current and detailed water quality information about your specific water system.

Official Source Links

The primary datasets and agency pages this page describes: