Methodology and limitations
How Tap Truth works
Tap Truth turns public federal drinking water records into a readable system record. It does not score systems or make a safety verdict. It shows the official violation history and lets the user decide what it means.
How it works
For address lookup, the app geocodes the address, tries to match the point against published EPA service-area boundaries first, and then falls back to ZIP and county lookup when no boundary match is available.
For system search, the user can search by system name, city, or ZIP code, pick the correct active community water system, and view the same violation record page.
Data sources
| Source | What it provides | Format |
|---|---|---|
| EPA ECHO SDWA Downloads | Full violation history for public water systems and system metadata. | CSV |
| Census Geocoder | Address to latitude and longitude for the lookup path. | REST |
| EPA Service Area Boundaries | Polygon boundaries used for point-in-polygon system matching when published coverage is available. | GeoJSON |
| Census ZCTA-to-county crosswalk | ZIP to county mapping for fallback lookup when polygon data is not available. | TXT |
What this tool does not do
- Does not test water quality. That requires lab analysis.
- Does not cover private wells. It only covers regulated public water systems.
- Does not use EWG's non-EPA standards.
- Does not give eligibility verdicts or safety opinions. It displays the federal record only.
- Is not a health advice or legal compliance tool.
Limitations
- Private wells are not covered because they are not regulated public water systems.
- The data is not real-time. It comes from public EPA downloads rather than live utility feeds.
- Tap Truth uses EPA service-area boundaries first when they are available, which is more accurate than ZIP-only matching.
- Not every public system has complete boundary coverage in the published EPA data, so some addresses still require ZIP and county fallback.
- Private wells, small private utilities, and unusual service areas can still be harder to match perfectly when boundary coverage is missing.
Verification
Tap Truth is an access layer over federal data. Users can verify any system directly in EPA ECHO.
View EPA ECHO drinking water data →