Water: Total Coliform Rule
Total Coliform Rule Requirements
1989 Total Coliform Rule
The Total Coliform Rule (TCR), a National Primary Drinking Water Regulation (NPDWR), was published in 1989 and became effective in 1990. The rule set both a health goal (Maximum Contaminant Level Goal, or MCLG) and legal limits (Maximum Contaminant Levels, or MCLs) for the presence of total coliforms in drinking water. EPA set the MCLG for total coliforms at zero because there have been waterborne disease outbreaks in which researchers found very low levels of coliforms, so any level indicates some health risk. The MCL levels are based on the positive sample tests for total coliforms (monthly MCL), or for total coliforms and Escherichia coli (E. coli) or fecal coliforms (acute MCL).
The purpose of the 1989 TCR is to protect public health by ensuring the integrity of the drinking water distribution system and monitoring for the presence of microbial contamination. The rule requires all public water systems (PWSs) to monitor for the presence of total coliforms in the distribution system at a frequency proportional to the number of people served. Systems which serve fewer than 1,000 people may test once a month or less frequently, while systems with 50,000 customers test at least 60 times per month and those with 2.5 million customers test at least 420 times per month. Water systems often take more than the required number of samples as a precaution.
To comply with the monthly MCL for total coliforms, PWSs must not find coliforms in more than five percent of the samples they take each month to meet EPA’s standards. If more than five percent of the samples contain coliforms, PWS operators must report this violation to the state and the public. If a sample tests positive for total coliforms, the system must collect a set of repeat samples located within 5 or fewer sampling sites adjacent to the location of the routine positive sample within 24 hours. When a routine or repeat sample tests positive for total coliforms, it must also be analyzed for fecal coliforms or E. coli, which are types of coliform bacteria that are directly associated with fresh feces. A positive result for fecal coliforms or E. coli can signify an acute MCL violation, which necessitates rapid state and public notification because it represents a direct health risk. Often, an acute violation due to the presence of fecal coliform or E. coli will result in a “boil water” notice. The system must also take at least 5 routine samples the next month of operation if any sample tests positive for total coliforms. To read the full requirements of the TCR, please see the Federal Register Notice of the rule from the link below.
For more information about coliforms and their health effects, please the TCR Basic Information page.
Quick Reference Guides
- Total Coliform Rule: A Quick Reference Guide PDF (2 pp, 114 K)
EPA 816-F-01-035, September 2001
- For other quick reference guides visit the drinking water standards - quick reference guides page.
The Total Coliform Rule (published 29 June 1989/effective 31 December 1990)
- Drinking Water Regulations; Total Coliforms (Including Fecal Coliforms and E. Coli); Final Rule PDF (26 pp, 5 M) (About PDF)
Revised Total Coliform Rule - Final Rule
On February 13, 2013, the Environmental Protection Agency (EPA) published revisions to the 1989 TCR. To learn more about the Revised Total Coliform Rule (RTCR), please see the TCR Revisions page.
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.