FAQ
Questions about the data
What's on the map, where it comes from, and how every number gets checked.
About the data
What is The Water Map?
A free, public map of what's actually in U.S. drinking water. Pick a contaminant — lead, PFAS, arsenic, nitrate — and every water system on the map colors by how its measured level compares to the federal limit. No signup, no paywall.
Where does the data come from?
From the water utilities themselves. Every community water system in the U.S. is required by federal law to publish an annual water-quality report — the Consumer Confidence Report, or CCR. We take those reports and put the numbers on a map. We don't run our own lab tests; we make the utilities' own data readable.
What is a Consumer Confidence Report?
It's the annual water-quality report your utility is legally required to deliver every year by July 1. It lists the contaminants they detected, the levels, and the federal limits. Most people never read theirs — it usually arrives as a dense PDF or a line on a bill. The whole point of this map is to make that report usable.
Which contaminants does the map cover?
Whatever the utility measured and reported. That spans metals like lead, copper and arsenic, disinfection byproducts like TTHM and HAA5, PFAS "forever chemicals," nitrate, fluoride, radionuclides and more. Use the contaminant picker at the top of the map to switch between them.
How it's verified
How do I know these numbers are right?
Every system has a 'View the original report' link on its page that opens the utility's source document. If a figure on the map ever looks surprising, you can check it against the source in one click. The numbers on the map are the utility's own — we transcribe, we don't audit.
Do you ever change a utility's numbers?
No. We transcribe each report as the utility published it. If a number on the map looks surprising, that's the utility's own reported figure — not our estimate. Every value stays traceable to the source document the report came from.
Reading the map
What do the marker colors mean?
Each marker is colored by the contaminant you've selected. Blue means the measured level is within the federal limit. Pink means it's approaching the limit, and a deeper pink means it's at or above the limit. Gray means the contaminant was detected but has no federal limit — or that the system didn't report it.
What is a "federal limit"?
For most contaminants the EPA sets a Maximum Contaminant Level (MCL) — the legal ceiling for that substance in drinking water. A few, like lead and copper, use an "action level" instead. The map compares each system's reported level to whichever standard applies.
Why does a system show "not measured"?
A utility only reports the contaminants it tested for. If a system is gray for, say, PFAS, its report didn't list a PFAS result — that doesn't necessarily mean PFAS is absent. Switch contaminants and you'll see coverage change from system to system.
Is this exactly what comes out of my tap?
Not exactly. A water-quality report covers an entire system or service area, not a single address. The map shows what your water provider measured across its supply. What reaches your specific faucet can still be affected by your home's own pipes and plumbing.
Scope and coverage
How often is the data updated?
The map grows as we verify more reports. A new water system appears the moment its report clears human review — so the map gets more complete over time, not on a fixed schedule.
Why isn't my city on the map yet?
We're adding systems steadily, starting with a verified core and expanding outward. Every U.S. community water system publishes a CCR, so any of them can be added — it just has to clear verification first.
Does the map cover microplastics?
Not in this dataset. Microplastics aren't federally regulated, so they don't appear in utilities' Consumer Confidence Reports. We do run a separate community microplastics project — you can see that data at /microplastics — but the main map here is the regulated water-quality data utilities are required to publish.
About the project
Is it free?
Yes. The map is completely free and public — no account, no paywall. The underlying reports are public record; we just make them readable.
Who is behind The Water Map?
It's an independent project with one job: take the water-quality data that already exists, verify it, and make it public on a map. We're not a utility, a filter company, or a lab.