E. coli
microbial contaminant
Human or animal fecal waste entering the source or distribution system.
EPA regulatory status
Legal limit (MCL)
No numeric MCL
Goal (MCLG)
0
Under the Revised Total Coliform Rule, an E. coli MCL violation is based on specified combinations of positive routine and repeat samples (presence-based), not a numeric concentration. MCLG = 0.
Health effects
E. coli in drinking water indicates recent fecal contamination. It can cause diarrhea, cramps, nausea, and, in vulnerable people, serious illness. Its presence signals that harmful pathogens may be present.
This is general public-health information, not medical advice — consult your physician with any health concerns.
National violations
46,739
EPA's enforcement data (SDWIS/ECHO) records 46,739 violations of E. coli's rule nationally.
How to remove E. coli
uv
NSF/ANSI 55
Frequently asked questions
What is E. coli?
E. coli is a microbial contaminant regulated in US drinking water. Human or animal fecal waste entering the source or distribution system.
What is the legal limit for E. coli in drinking water?
Under the Revised Total Coliform Rule, an E. coli MCL violation is based on specified combinations of positive routine and repeat samples (presence-based), not a numeric concentration. MCLG = 0.
What health effects does E. coli have?
E. coli in drinking water indicates recent fecal contamination. It can cause diarrhea, cramps, nausea, and, in vulnerable people, serious illness. Its presence signals that harmful pathogens may be present.
How many violations of E. coli limits are on record nationally?
EPA's enforcement data (SDWIS/ECHO) records 46,739 violations of E. coli's rule nationally.
How do I remove E. coli from my water?
Filter technologies certified to reduce E. coli 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