Open dataset
U.S. drinking water — every contaminant, every federal limit, in one dataset.
Every number on this site is transcribed from a utility's own annual drinking-water report and compared to the federal limit. Free to read, free to query, free to redistribute. CC BY 4.0.
0
Water systems
approved + on the map
0
States
and counting
0
Contaminants
0 families
0
Measured values
reports —
Get the data
Map (HTML)Web
Pan, click a city, get its full structured report. Designed for humans.
Open →
Index of city pagesHTML
Every approved system — 0 URLs, one per city/year, each rendered as a structured HTML table.
Open →
JSON APIJSON
No key, no rate limit. List endpoint + per-system endpoint. Documented at /api-access.
Open →
Markdown for LLMsMarkdown
Site-wide Markdown index per the llms.txt convention. Every city page has its own /water/.../llms.txt twin.
Open →
MCP serverMCP
Wire The Water Map straight into Claude or Cursor. Your assistant answers questions from the live dataset.
Open →
SitemapXML
Every URL in the dataset, machine-readable. Use it as a crawl seed.
Open →
How the data is built
Every U.S. public water utility is required to publish an annual Consumer Confidence Report. We collect those PDFs, transcribe each contaminant measurement into a structured row, and surface it on a per-city page alongside the federal limit. The source document is archived and linked from every page so any figure can be checked.
Contaminant rollup logic, the "over the limit" threshold, and the federal-standard preference rules are documented in the code and on the API page.
Related dataset
Microplastics in LA tap water →
A separate lab-counted dataset: particle counts in samples we ran under a microscope. No federal limit exists yet.