Revised Total Coliform Rule
What this EPA rule requires, what a violation means for you, and what to do about it.
📜 What This Rule Is
The Total Coliform Rule, first issued by the EPA in 1989 and revised in 2013, protects against microbial contamination of drinking water. Total coliforms are a group of related bacteria that are, with few exceptions, not themselves harmful. The EPA uses them as an indicator: their presence signals that a treatment or distribution-system problem may be letting other, genuinely harmful pathogens through. The Revised Total Coliform Rule (RTCR) took effect on April 1, 2016 and applies to every public water system.
⚙️ What It Requires of Your Water System
Systems must follow a written sample siting plan and collect routine samples on a schedule set by how many people they serve. Any sample that is total-coliform-positive must be re-sampled within 24 hours at nearby sites and analyzed for E. coli. The rule sets a Maximum Contaminant Level of zero for E. coli and, for total coliforms, a treatment-technique requirement: when results cross a set frequency, the system must perform a Level 1 or Level 2 assessment of its system and fix any sanitary defect it finds.
⚠️ What a Violation Means for You
Most Total Coliform Rule violations are monitoring, reporting, or assessment failures — the system missed a sample, filed late, or did not complete a required assessment on time. These are indicator and paperwork problems, not evidence that your water made anyone sick. The serious exception is an E. coli Maximum Contaminant Level violation, which signals possible fecal contamination and triggers an immediate public notice, sometimes a boil-water advisory. Check whether the violation is an E. coli MCL violation or a monitoring/assessment violation; the two mean very different things.
🩺 Health Context
Total coliforms themselves rarely cause illness, but they flag conditions under which bacteria, viruses, and parasites could enter the water. E. coli, a specific type detected under this rule, indicates recent fecal contamination and a real risk of gastrointestinal illness. People with weakened immune systems, infants, and the elderly are most vulnerable to waterborne pathogens.
🕑 Rule History
The EPA published the original Total Coliform Rule in 1989 (effective 1990), setting a Maximum Contaminant Level Goal of zero. The Revised Total Coliform Rule was published on February 13, 2013 with compliance required from April 1, 2016. Its central change was to drop the monthly total-coliform MCL in favor of the find-and-fix Level 1 / Level 2 assessment approach, while keeping the zero MCL for E. coli.
✅ What You Can Do
If your system reports an E. coli MCL violation, follow any boil-water notice exactly and use bottled or boiled water until the system reports it is resolved. For a monitoring or assessment violation, no action is usually needed, but you can ask your utility what sample was missed and whether an assessment found a defect. Boiling water for one minute kills coliform bacteria; a filter alone does not.
Revised Total Coliform Rule: Frequently Asked Questions
What is the Revised Total Coliform Rule?
The Total Coliform Rule, first issued by the EPA in 1989 and revised in 2013, protects against microbial contamination of drinking water. Total coliforms are a group of related bacteria that are, with few exceptions, not themselves harmful. The EPA uses them as an indicator: their presence signals that a treatment or distribution-system problem may be letting other, genuinely harmful pathogens through. The Revised Total Coliform Rule (RTCR) took effect on April 1, 2016 and applies to every public water system.
What does a Total Coliform Rule violation mean for my drinking water?
Most Total Coliform Rule violations are monitoring, reporting, or assessment failures — the system missed a sample, filed late, or did not complete a required assessment on time. These are indicator and paperwork problems, not evidence that your water made anyone sick. The serious exception is an E. coli Maximum Contaminant Level violation, which signals possible fecal contamination and triggers an immediate public notice, sometimes a boil-water advisory. Check whether the violation is an E. coli MCL violation or a monitoring/assessment violation; the two mean very different things.
What should I do about a Total Coliform Rule violation?
If your system reports an E. coli MCL violation, follow any boil-water notice exactly and use bottled or boiled water until the system reports it is resolved. For a monitoring or assessment violation, no action is usually needed, but you can ask your utility what sample was missed and whether an assessment found a defect. Boiling water for one minute kills coliform bacteria; a filter alone does not.
🔗 Related Rules
💧 Related Contaminants
Check your water system's violation history
Search your ZIP code to see whether your water system has any Total Coliform Rule violations on record, plus an overall safety grade and lead testing results.
Search your ZIP code →Rule descriptions are drawn from the EPA's drinking water regulation pages. Violation records come from the EPA's Safe Drinking Water Information System (SDWIS).