E. coli in U.S. Drinking Water

E. coli is regulated under the EPA Safe Drinking Water Act, which sets enforceable Maximum Contaminant Levels (MCLs) and associated treatment technique requirements for public water systems. The EPA Safe Drinking Water Information System (SDWIS) tracks every recorded violation nationwide and links it back to the specific public water system (PWSID), violation type, and begin date.

Across the United States, SDWIS records show 35,382 health-based violations for E. coli affecting 12,867 community water systems in 56 states. Violation counts cluster heaviest in Pennsylvania, Texas, Arizona, with Pennsylvania alone accounting for 473 violations across 153 systems. EPA health-effect summaries describe the specific exposure concerns that drove the federal standard.

A health-based violation does not mean residents were necessarily harmed, it means the contaminant exceeded the federal MCL in a compliance sample, triggering notification and remediation requirements. States and utilities maintain primary enforcement responsibility. To check the status of a specific water system, request its most recent Consumer Confidence Report or consult the EPA's Drinking Water Watch portal for the corresponding state.