Provenance · public records · limitations
Our Data Sources
The public datasets behind every finding, and how fresh they are. Every report keeps the relevant publisher, dates, units, qualifiers, and evidence identifiers attached to the finding.
Source classes used by PurityMap
These cards describe the governed source categories, not a claim that every system has every source. Individual report pages list the documents actually used.
Source class 01
EPA SDWIS
The Safe Drinking Water Information System supplies public-water-system inventory and compliance monitoring, including lead and copper (LCR) results.
Source class 02
UCMR5
The fifth Unregulated Contaminant Monitoring Rule provides nationwide occurrence data for PFAS and other emerging contaminants — the basis for our PFAS findings.
Source class 03
Utility Consumer Confidence Reports
Annual CCRs published by utilities supply hardness, disinfectant type and additional analyte results that federal datasets do not always carry.
Source class 04
Census geography
Census TIGER place files resolve city and place names to the systems that serve them.
What stays attached to a finding
Freshness
Each finding carries its own sampling and publication dates. Where a system’s record is stale or sparse, we say so rather than filling the gap.
How to inspect provenance
- 01
Start with a report
Resolve the supplier serving a place and open its published water record.
- 02
Read the finding
Check the sample date, unit, qualifier, benchmark, and evidence state.
- 03
Open the source
Use the linked evidence or source record to inspect provenance and limitations.