Total Coliform in U.S. Drinking Water
Health-based violation data for Total Coliform from EPA Safe Drinking Water Information System (SDWIS). Covers all community water systems with violations on record.
Total Coliform has been found in violation of EPA standards in 3,385 water systems across 17 states, with 8,765 total health-based violations recorded. The most affected states are Oklahoma, Nebraska, California.
Total Coliform 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 8,765 health-based violations for Total Coliform affecting 3,385 community water systems in 17 states. Violation counts cluster heaviest in Oklahoma, Nebraska, California, with Oklahoma alone accounting for 1,517 violations across 457 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.
What are the health effects of this contaminant?
Total coliform bacteria signal potential contamination pathways. While most coliforms are not harmful, their presence indicates the water treatment system may be compromised.
Source: U.S. Environmental Protection Agency. Consult your doctor for personalized health guidance U.S. Environmental Protection Agency. Consult your doctor for personalized health guidance
Violations by State
States ranked by number of health-based violations for Total Coliform.
| # | State | Violations | Systems Affected |
|---|---|---|---|
| 1 | Oklahoma | 1,517 | 457 |
| 2 | Nebraska | 244 | 127 |
| 3 | California | 13 | 7 |
| 4 | Iowa | 12 | 1 |
| 5 | Louisiana | 12 | 4 |
| 6 | Kansas | 9 | 2 |
| 7 | Texas | 8 | 4 |
| 8 | Arkansas | 7 | 1 |
| 9 | West Virginia | 5 | 3 |
| 10 | Colorado | 4 | 1 |
| 11 | Oregon | 4 | 1 |
| 12 | Idaho | 3 | 1 |
| 13 | Nevada | 2 | 1 |
| 14 | South Dakota | 2 | 1 |
| 15 | Tennessee | 2 | 1 |
| 16 | Washington | 2 | 1 |
| 17 | New Jersey | 1 | 1 |
Most Affected Water Systems
Top 50 water systems by number of Total Coliform health-based violations.
Frequently Asked Questions
Is Total Coliform in my water?
Total Coliform has been detected in violation of EPA health standards in 3,385 water systems across 17 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 Total Coliform violations?
EPA SDWIS records show 3,385 community water systems with health-based Total Coliform violations, totaling 8,765 violations. These represent cases where the contaminant exceeded the EPA Maximum Contaminant Level (MCL).
Which states have the most Total Coliform violations?
The states with the most Total Coliform violations are: Oklahoma (1,517 violations), Nebraska (244 violations), California (13 violations), Iowa (12 violations), Louisiana (12 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.