EPA SDWIS — reading drinking-water violations without panicking

What SDWIS is

The Safe Drinking Water Information System is EPA's national clearinghouse for public-water-system compliance data, updated quarterly with state submissions.

It covers every water system that serves 25+ people or has 15+ service connections — which is virtually all municipal and most rural water in the US.

Three kinds of violation

Health-based violations — contaminant levels exceeded an enforceable Maximum Contaminant Level (MCL). These are the ones that matter most.

Treatment-technique violations — the system didn't run required treatment processes (disinfection, filtration). Usually procedural; sometimes serious.

Reporting + monitoring violations — the system didn't sample or report on time. Common, often paperwork-only, but recurring failures suggest weak management.

Lead and copper

Under the Lead and Copper Rule (LCR) and 2024 LCRR revisions, systems must sample household taps and report 90th-percentile lead levels. Action level: 15 ppb (dropping to 10 ppb under LCRI).

If your system exceeds the action level, replacement of lead service lines becomes mandatory. We surface this status on every ZIP page where the data exists.

What SDWIS won't tell you

Private well water — fully outside EPA's public-system jurisdiction. If you're on a well, you're responsible for testing, every year.

Plumbing in your specific home — corrosion in your service line or fixtures can leach lead even if the utility is clean. Buy a $25 home test kit if it matters.

Taste, smell, hardness, fluoride preference — these are not 'violations,' just preferences.

What zipradar shows

Primary water utility serving the ZIP, current violation count by category, lead/copper compliance status, and links to the full SDWIS detail page for that PWSID.

Quarterly refresh from EPA. Fingerprint timestamp on each page tells you the exact data vintage.