Methodology & data sources
Dataset updated .
Source data
AquaCensus is built from the U.S. EPA's Safe Drinking Water Information System (SDWIS), obtained through the EPA ECHO bulk data service (SDWA dataset). The inventory covers 143,021 active public water systems — system name, PWSID, system type, primacy agency, population served, service connections, owner type, primary water source and served geography (city, county, state, ZIP).
SDWA violation and enforcement records (also from EPA ECHO) are being ingested and will appear on system profiles; until then, profiles link to EPA ECHO for compliance history.
Refresh cadence
EPA publishes the SDWA bulk dataset quarterly. AquaCensus re-syncs on that cadence with id-stable upserts keyed on PWSID, and every page carries a machine-readable "Dataset updated" timestamp plus Dataset JSON-LD with dateModified.
Definitions & caveats
- Only systems with EPA activity status "A" (active) are indexed; inactive systems resolve but are excluded from search indexing and sitemaps.
- "Population served" is the figure each system reports to its primacy agency; summing across systems double-counts people served by wholesalers and purchasers.
- Geography comes from EPA's geographic-areas records; where a system spans multiple areas, the first reported county/city is used. EPA does not publish coordinates for water systems.
- AquaCensus is screening data, not compliance or health advice. For current compliance status, consult EPA ECHO or the system's Consumer Confidence Report.
Licensing & attribution
Underlying EPA records are U.S. public data. AquaCensus pages and derived aggregates may be cited with attribution to "AquaCensus (aquacensus.com)". For bulk or API access, contact kenny@hyder.me.