Chlorine in U.S. Drinking Water
Health-based violation data for Chlorine from EPA Safe Drinking Water Information System (SDWIS). Covers all community water systems with violations on record.
Chlorine has been found in violation of EPA standards in 1,662 water systems across 42 states, with 4,490 total health-based violations recorded. The most affected states are Arkansas, South Dakota, Colorado.
Chlorine 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 4,490 health-based violations for Chlorine affecting 1,662 community water systems in 42 states. Violation counts cluster heaviest in Arkansas, South Dakota, Colorado, with Arkansas alone accounting for 1,569 violations across 127 systems. The contaminant is listed on the federal primary drinking water regulations.
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.
Violations by State
States ranked by number of health-based violations for Chlorine.
| # | State | Violations | Systems Affected |
|---|---|---|---|
| 1 | Arkansas | 1,569 | 127 |
| 2 | South Dakota | 534 | 207 |
| 3 | Colorado | 316 | 175 |
| 4 | New York | 177 | 124 |
| 5 | Wisconsin | 131 | 72 |
| 6 | Missouri | 127 | 63 |
| 7 | Virginia | 99 | 70 |
| 8 | West Virginia | 69 | 39 |
| 9 | California | 63 | 37 |
| 10 | Michigan | 44 | 29 |
| 11 | Indiana | 43 | 20 |
| 12 | Minnesota | 27 | 11 |
| 13 | Massachusetts | 26 | 14 |
| 14 | Georgia | 18 | 17 |
| 15 | New Mexico | 18 | 15 |
| 16 | Wyoming | 16 | 2 |
| 17 | Oregon | 11 | 6 |
| 18 | Tennessee | 11 | 5 |
| 19 | Ohio | 10 | 7 |
| 20 | New Jersey | 9 | 9 |
| 21 | Pennsylvania | 9 | 4 |
| 22 | South Carolina | 9 | 2 |
| 23 | Delaware | 8 | 7 |
| 24 | Iowa | 8 | 4 |
| 25 | Kentucky | 7 | 5 |
| 26 | Kansas | 6 | 4 |
| 27 | Alaska | 4 | 3 |
| 28 | Nevada | 4 | 3 |
| 29 | Rhode Island | 4 | 2 |
| 30 | Vermont | 4 | 4 |
| 31 | Florida | 3 | 3 |
| 32 | Idaho | 3 | 1 |
| 33 | Illinois | 3 | 2 |
| 34 | Maine | 3 | 2 |
| 35 | Maryland | 3 | 3 |
| 36 | Texas | 3 | 1 |
| 37 | Louisiana | 2 | 2 |
| 38 | Nebraska | 2 | 2 |
| 39 | Arizona | 1 | 1 |
| 40 | Oklahoma | 1 | 1 |
| 41 | Washington | 1 | 1 |
| 42 | Northern Mariana Islands | 1 | 1 |
Most Affected Water Systems
Top 50 water systems by number of Chlorine health-based violations.
Frequently Asked Questions
Is Chlorine in my water?
Chlorine has been detected in violation of EPA health standards in 1,662 water systems across 42 states. To check your specific utility, look up your annual Consumer Confidence Report (CCR) - water systems are required to disclose all violations.
How many water systems have Chlorine violations?
EPA SDWIS records show 1,662 community water systems with health-based Chlorine violations, totaling 4,490 violations. These represent cases where the contaminant exceeded the EPA Maximum Contaminant Level (MCL).
Which states have the most Chlorine violations?
The states with the most Chlorine violations are: Arkansas (1,569 violations), South Dakota (534 violations), Colorado (316 violations), New York (177 violations), Wisconsin (131 violations).
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About This Data
Violation data is from the EPA Safe Drinking Water Information System (SDWIS). Only health-based violations are shown, these include Maximum Contaminant Level (MCL) and Treatment Technique (TT) violations. Monitoring and reporting violations are excluded. Data may not reflect the most current enforcement actions.
Source: U.S. Environmental Protection Agency, SDWIS Federal Reporting Services U.S. Environmental Protection Agency, SDWIS Federal Reporting Services
Read our methodology - how this data is sourced, computed, and verified.