Total Coliform Bacteria in Drinking Water

EPA Limit: Presence in >5% of monthly samples

Under the Revised Total Coliform Rule (RTCR), water systems must test for total coliforms and E. coli. A system triggers a violation when total coliforms are found in more than 5% of monthly routine samples.

Where Does Total Coliform Bacteria Come From?

Coliform bacteria are found naturally in soil, water, and the intestines of animals. While most coliform bacteria are not harmful themselves, their presence in treated drinking water indicates that the treatment or distribution system may be compromised, potentially allowing disease-causing organisms to enter the water supply.

Health Risks

Total coliform bacteria are indicator organisms — their presence suggests that pathogenic bacteria, viruses, or parasites may also be present. Actual health effects depend on which specific pathogens are present and can range from gastrointestinal illness to more serious infections.

What Should I Do?

If your water system has coliform violations, consider boiling water or using bottled water until the system confirms the issue is resolved. Contact your water provider for their latest test results and any boil-water advisories.