Coliform bacteria in drinking water
Also called E. coli, coliform.
Indicator bacteria. A violation means the system found coliform or E. coli and had to investigate or fix the cause.
Health: E. coli means fecal contamination and can cause illness. Follow any boil-water notice.
Across the US
2,572 community water systems had at least one health-based Coliform bacteria violation since 2016. Routine Coliform bacteria sample results are reported to states, not to EPA's national database, so this page ranks systems by violations rather than levels.
Most violations
| Water system | People | Violations |
|---|---|---|
| Chapelle MDWCA | 60 | 24 |
| Grindstone Rancheria Water System | 150 | 20 |
| SCUA Upper Seven Mile | 8,478 | 15 |
| Grayling Water System | 207 | 15 |
| Central ASG | 45,315 | 14 |
| PRASA – Anon Carmelita | 900 | 13 |
| River Point Water System | 45 | 13 |
| Lakeview Trailer Park Water System | 30 | 12 |
| Maple Elsie Water Service | 100 | 11 |
| Southgate MHP Water System | 177 | 10 |
| Big Bass Lake Water Association | 130 | 10 |
| Starlight Village Water System | 65 | 10 |
| Banida Water and Sewer District | 180 | 9 |
| Juniper Club Inc. | 104 | 9 |
| Manor Water Associations | 75 | 9 |
| Port Protection Water System | 60 | 9 |
| Chenega Water System | 50 | 9 |
| Foster Senior Housing Inc. | 31 | 9 |
| Belleville Water Dept | 35,129 | 8 |
| SCUA Bylas | 3,160 | 8 |
| My Place Mobile Home Park Water System | 111 | 8 |
| Ramsey Estates Water System | 88 | 8 |
| Hilltop Village Association | 86 | 8 |
| PRASA – Zamas | 1,200 | 7 |
| Lorraine Village Water System | 1,008 | 7 |
States with the most systems with violations
- Texas: 199
- Pennsylvania: 176
- Arizona: 143
- California: 131
- Oregon: 124
- Missouri: 108
- Idaho: 105
- Washington: 81
- Nebraska: 80
- Puerto Rico: 77
- Connecticut: 77
- New Hampshire: 77
Sources
The limits, health goals and health effects on this page come from these EPA sources. The results come from EPA's monitoring data for each water system.
- EPA: National Primary Drinking Water Regulations (limits and health effects table)
- EPA: Emergency disinfection of drinking water
- EPA ECHO: Safe Drinking Water Information System data
This page summarizes public regulatory information. It is not medical advice. How we source and check this site.
Questions
How do I remove Coliform bacteria from tap water?
See the filter guidance on this page: look for a product certified for Coliform bacteria specifically, and check the claim in NSF's certified product listings.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.