Total Coliform in Drinking Water

Total coliform bacteria are a broad group of organisms that are naturally present in the environment -- in soil, on vegetation, and in the intestines of warm-blooded animals. Most coliform bacteria are not harmful by themselves, but their presence in treated drinking water serves as a critical warning sign. Finding total coliforms in your water means that the treatment system or distribution network has a vulnerability that could allow disease-causing organisms to enter. Think of it as a canary in the coal mine: the coliforms themselves may not make you sick, but they indicate that the door is open for pathogens that will.

Under the EPA's Revised Total Coliform Rule (RTCR), any detection of total coliforms in a routine sample triggers additional testing requirements. If E. coli is found in follow-up testing, that indicates direct fecal contamination and an immediate public health risk. Water systems with repeated total coliform detections must investigate and correct the underlying cause, whether it's a cracked pipe, insufficient disinfection, or cross-connection with a contaminated source.

For private well owners, total coliform testing is the single most important water quality test you can perform. Wells can become contaminated through cracks in the well casing, improper sealing around the wellhead, or flooding events. A positive total coliform test doesn't necessarily mean your water will make you sick, but it does mean you should take action: disinfect the well through shock chlorination, retest, and if the problem persists, investigate the physical integrity of your well system.