Total Coliforms

Category: microbiological

Written by WaterFilterMatch Editorial TeamApril 2026

EPA MCL

Not regulated

Status

EPA Regulated

NSF Standard

NSF/ANSI 55 (UV), NSF/ANSI 58

Health Effects

Total coliforms are indicator organisms - their presence suggests the water system may be vulnerable to contamination by more harmful pathogens. Not necessarily harmful themselves, but a warning sign for potential fecal contamination.

Source: EPA National Primary Drinking Water Regulations

Where It Comes From

Naturally present in the environment (soil, vegetation). In drinking water, their presence indicates inadequate treatment, a breach in the distribution system, or a contamination event.

Where It's Commonly Found

Can occur in any water system, especially after main breaks, treatment failures, or in systems with aging infrastructure. More common in small or rural systems.

Regulated under the 2013 Revised Total Coliform Rule (RTCR). Systems with coliform detections must conduct assessments and corrective actions. Treatment technique - no numeric MCL.