U.S. safety records, as the agencies wrote them. Independent.
Tap water · contaminant or rule

Groundwater Rule in drinking water

The community water systems with a health-based violation of Groundwater Rule on EPA's record since Oct. 23, 2023, most people served first. EPA's file dated Oct. 23, 2026.

1,532

1,532 systems serving 3,421,597 people in 40 states and territories.

Health-based violations, in EPA's words: “Violations of maximum contaminant levels (MCLs) or maximum residual disinfectant levels (MRDLs), which specify the highest concentrations of contaminants or disinfectants, respectively, allowed in drinking water; or of treatment technique (TT) rules, which specify required processes intended to reduce the amounts of contaminants in drinking water. MCLs, MRDLs, and treatment technique rules are all health-based drinking water standards.”

By state

Louisiana 260Pennsylvania 215New Mexico 197Arizona 130Alaska 67Missouri 62Indiana 48West Virginia 46Colorado 46Idaho 44Utah 39Wyoming 36Mississippi 34California 32Nevada 31Wisconsin 29Washington 27Ohio 23New Hampshire 22Montana 16Texas 15Oregon 14Michigan 14Kansas 13Connecticut 11New York 11Minnesota 9Virginia 8South Dakota 5District of Columbia 5Maryland 4Northern Mariana Islands 4New Jersey 3Massachusetts 3Arkansas 2Rhode Island 2Nebraska 2North Dakota 1Iowa 1Georgia 1

Systems

The 300 systems serving the most people are listed here; every one of the 1,532 is on its state's page (the states above).

From EPA's Safe Drinking Water Information System (SDWIS), through EPA ECHO's drinking water system download. Health-based violations from EPA Envirofacts, downloaded Nov. 2, 2026. EPA's file dated Oct. 23, 2026. EPA: “All compliance and enforcement data displayed on ECHO are current as of the last official quarterly refresh of the source data system, SDWIS, which may lag by three to six months.” These are records of violations, not a test of your tap water today: your water system's annual Consumer Confidence Report has its test results. Names and values are shown as EPA writes them. EPA ECHO drinking water search.