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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.
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
- 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)
- June 29, 1989 Federal Register Notice PDF (26 pp, 5 M) (About PDF)
Notice of Intent to Revise the Total Coliform Rule
EPA is required to review existing national primary drinking water regulations every six years. In 2003, EPA completed its review of the Total Coliform Rule (TCR) and 68 NPDWRs for chemicals that were established prior to 1997. The purpose of the review was to identify current health risk assessments, changes in technology, and other factors that would provide a health or technological basis to support a regulatory revision that will maintain or improve public health protection. In the 2003 announcement of the completion of the Six Year Review, EPA noticed its intent to revise the Total Coliform Rule. As part of the TCR rulemaking, EPA plans to assess the effectiveness of the current TCR in reducing public health risk, and what technically supportable alternative/additional monitoring strategies are available that would decrease economic burden while maintaining or improving public health protection. In response to recommendations from the Stage 2 M/DBP Federal Advisory Committee (see below), the Agency will also consider if and how risks associated with distribution systems should be addressed.
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.