All natural waters are contaminated to some degree with bacteria. Generally, these bacteria are harmless to humans and are essential to the breakdown of organic materials found in water. However, when a water source is polluted with human or animal wastes, it may contain microbial organisms that cause illness.

Coliform bacteria are found in the intestines of humans and animals, and their presence in a water supply suggests possible pollution with disease-causing organisms. The Total Coliform Bacteria test is used as an indicator of the bacterial safety of your drinking water. The EPA states that drinking water should not contain any coliform bacteria. If coliforms are found, the water supply is considered a potential health hazard and is classified as "UNSAFE" for human consumption.

Contamination of an existing system can be caused by inadequate disinfection after construction or maintenance work. After repairing a pump in an existing well, for example, the water may be temporarily contaminated with coliform bacteria, which are present in soil, vegetation, and on the tools and hands of the maintenance crew. The entire system should be flushed out, disinfected, and sampled for coliforms prior to being put back into service. See instructions for "Well Chlorination."

The standard coliform bacteria test shows the difference between coliforms of fecal origin, specifically E. coli, and coliforms from other sources. Drinking water contaminated with E. coli is considered an "extreme health hazard."

Your Total Coliform test results are reported as "Absent" or "Present." Please see Interpreting the Coliform Bacteria Test Results.

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