Total Coliform Bacteria
microbial contaminant
Naturally present in the environment and in soil; intrusion into the distribution system through breaks, low pressure, or inadequate disinfection.
EPA regulatory status
Legal limit (MCL)
No numeric MCL
Goal (MCLG)
0
No numeric MCL under the Revised Total Coliform Rule (RTCR, effective 2016). Total coliform detections trigger assessment and corrective-action requirements (a treatment-technique approach). MCLG = 0. (This replaced the obsolete pre-2016 rule that allowed no more than 5% positive samples.)
Health effects
Total coliforms are generally not harmful themselves, but their presence indicates that the treatment or distribution system may be vulnerable to contamination by disease-causing organisms.
This is general public-health information, not medical advice — consult your physician with any health concerns.
National violations
1,151,686
EPA's enforcement data (SDWIS/ECHO) records 1,151,686 violations of Total Coliform Bacteria's rule nationally.
How to remove Total Coliform Bacteria
uv
NSF/ANSI 55
Frequently asked questions
What is Total Coliform Bacteria?
Total Coliform Bacteria is a microbial contaminant regulated in US drinking water. Naturally present in the environment and in soil; intrusion into the distribution system through breaks, low pressure, or inadequate disinfection.
What is the legal limit for Total Coliform Bacteria in drinking water?
No numeric MCL under the Revised Total Coliform Rule (RTCR, effective 2016). Total coliform detections trigger assessment and corrective-action requirements (a treatment-technique approach). MCLG = 0. (This replaced the obsolete pre-2016 rule that allowed no more than 5% positive samples.)
What health effects does Total Coliform Bacteria have?
Total coliforms are generally not harmful themselves, but their presence indicates that the treatment or distribution system may be vulnerable to contamination by disease-causing organisms.
How many violations of Total Coliform Bacteria limits are on record nationally?
EPA's enforcement data (SDWIS/ECHO) records 1,151,686 violations of Total Coliform Bacteria's rule nationally.
How do I remove Total Coliform Bacteria from my water?
Filter technologies certified to reduce Total Coliform Bacteria include: uv (NSF/ANSI 55), reverse osmosis (NSF/ANSI 58). Look for a filter independently certified against the specific NSF/ANSI standard for this contaminant — general "reduces contaminants" marketing claims are not the same as a contaminant-specific certification.
Source: EPA National Primary Drinking Water Regulations · Data as of 2026-07-16