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Water: Total Coliform Rule

Total Coliform Rule

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The Total Coliform Rule was published in 1989 and became effective in 1990.  The rule set both health goals (MCLGs) and legal limits (MCLs) for the presence  of total coliform in drinking water.  The rule also detailed the type and frequency of testing that water systems must undertake.  In 2003, EPA announced its intent to revise the Total Coliform Rule.

TCR Issue Papers

To learn more about the TCR Issue Papers and Federal Advisory Committee that contributed to the development of the rule revisions, please see the TCR Revisions page.

2010 Proposed Revisions to the Total Coliform Rule

The Environmental Protection Agency (EPA) is proposing revisions to the 1989 Total Coliform Rule (TCR), a national primary drinking water regulation (NPDWR). The purpose of the TCR is to protect public health by ensuring the integrity of the drinking water distribution system and monitoring for the presence of microbial contamination. EPA anticipates greater public health protection under the proposed revised requirements, which are based on recommendations by a federal advisory committee. The proposed revisions to the TCR will:

  • require public water systems that are vulnerable to microbial contamination to identify and fix problems, and
  • establish criteria for systems to qualify for and stay on reduced monitoring, thereby providing incentives for improved water system operation.

Federal Register Notice and supporting documents

Proposed Revised Total Coliform Rule Assessments and Corrective Actions Guidance Manual, Draft
EPA 815-D-10-001, August 2010
Status: Draft guidance manual for public review and comment
Description: The draft guidance manual provides public water systems and primacy agencies with guidance on complying with and implementing the assessment and corrective action requirements of the proposed Revised Total Coliform Rule (RTCR). Under the proposed RTCR, public water systems that are vulnerable to microbial contamination in the distribution system (as indicated by their monitoring results for total coliforms and E. coli) are required to assess the problem and take corrective action that may reduce cases of illnesses and deaths due to potential fecal contamination and waterborne pathogen exposure. The draft guidance manual provides information on how to conduct assessments to identify the causes of total coliform and E. coli occurrence in the distribution system, and on the corresponding corrective actions that systems can take to correct the problem.

Please submit comments and suggestions to prtcr_acaguide@epa.gov by November 30, 2010.

Target audience: Public water systems, States, Primacy agencies.

Recommendations from Stage 2 M/DBP Agreement in Principle on Distribution Systems

In 2000, as part of its recommendations concerning the Long-Term 2 Enhanced Surface Water Treatment Rule and the Stage 2 Disinfection Byproducts Rule, the Stage 2 Microbial/Disinfection Byproducts (M/DBP) Federal Advisory Committee recognized the following points in its Agreement in Principle

  • "Finished water storage and distribution systems may have an impact on water quality and may pose risks to public health."
  • "Cross-connections and backflow in distribution systems represent a significant public health risk."
  • "Water quality problems can be related to infrastructure problems and that aging of distribution systems may increase risks of infrastructure problems."
  • "Distribution systems are highly complex and that there is a significant need for additional information and analysis on the nature and magnitude of risk associated with them."

The FACA concluded that EPA should review and evaluate available data and research on those aspects of distribution systems that may create or pose risks to public health as a part of the Six-Year Review of the TCR. The FACA also concluded that EPA should initiate a process with stakeholder participation for addressing requirements for cross-connection control and backflow prevention, and distribution systems issues related to significant health risks.

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1989 Total Coliform Rule

The TCR requires all public water systems (PWSs) to monitor for the presence of total coliforms in the distribution system. 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 most bacterial pathogens and many viral enteric pathogens, EPA considers them a useful indicator of these pathogens. More important, 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.
The TCR requires systems to monitor for total coliforms at a frequency proportional to the number of people served. If any sample tests positive for total coliforms, the system must perform the following additional tests:

  • Further test that culture for the presence of either fecal coliforms or Escherichia coli;
  • Take one set of 3-4 repeat samples at sites located within 5 or fewer sampling sites adjacent to the location of the routine positive sample within 24 hours; and
  • Take at least 5 routine samples the next month of operation
Quick Reference Guides

The Total Coliform Rule (published 29 June 1989/effective 31 December 1990)

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