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Water: Total Coliform Rule

Basic Information

There are a variety of bacteria, parasites, and viruses which can potentially cause health problems if humans ingest them in drinking water. Testing water for each of these potential pathogens (disease causing agents) would be difficult and expensive. Instead, water quality and public health workers measure coliform levels. The presence of any coliforms in drinking water suggests that there may be a pathway for pathogens and/or fecal contamination to enter the drinking water distribution system (pipes, storage facilities, etc.).

Total coliforms are a group of closely related bacteria that are (with few exceptions) not harmful to humans.  Because total coliforms are common inhabitants of ambient water and may be injured by environmental stresses (e.g., lack of nutrients) and water treatment (e.g., chlorine disinfection) in a manner similar to many pathogens, EPA considers them a useful indicator of these pathogens.  Health problems associated with these pathogens include diarrhea, cramps, nausea and vomiting.  Together these symptoms comprise a general category known as gastroenteritis.  Gastroenteritis is not usually serious for a healthy person, but it can lead to more serious problems for people with weakened immune systems, such as the very young, elderly, or immuno-compromised.

For drinking water, total coliforms are used to determine the adequacy of water treatment and the integrity of the distribution system.  The absence of total coliforms in the distribution system minimizes the likelihood that fecal pathogens are present.  Thus, total coliforms are used to determine the vulnerability of a system to fecal contamination.

EPA published the Total Coliform Rule (TCR) in 1989 to protect against fecal contamination and it became effective in 1990.  To learn more about the 1989 TCR, please see the TCR page.

On February 13, 2013, EPA revised the 1989 TCR.  EPA anticipates greater public health protection under the Revised Total Coliform Rule (RTCR) requirements, which are largely based on recommendations by a federal advisory committee.  Public water systems (PWSs) and primacy agencies must comply with the requirements of the Revised Total Coliform Rule (RTCR) by April 1, 2016.  Until then, PWSs and primacy agencies must continue complying with the 1989 TCR.  To learn more about the RTCR, please see the TCR Revisions page.


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