Revised Total Coliform Rule | Drinking Water Compliance Assistance

The Revised Total Coliform Rule (RTCR) establishes a maximum contaminant level (MCL) for E. coli and uses E. coli and total coliforms to initiate a “find and fix” approach to address fecal contamination that could enter into the distribution system. It requires public water systems (PWSs) to perform assessments to identify sanitary defects and subsequently take action to correct them.

What to Do If There's an Exceedance

Total Coliform Positive
If the system gets notification of a routine total coliform positive result, they must take three repeat samples (original site, upstream site and downstream site) as specified in their Microbiological Sample Siting Plan (MSSP). Groundwater systems also require a RAW water source sample from all ground water sources that were active and contributed to the finished water at the time of the original positive coliform sample. 

If E. coli tests positive:

  • Contact ADEQ by the end of the business day or within 24 hours if the business day has already ended
  • Take necessary repeats and triggered samples and notify your Compliance Assistance Coordinator about results
  • Submit a copy of your system’s MSSP to ADEQ, if you have not done so already

Repeat and triggered samples must be taken within 24 hours notification from the laboratory. If 24 hours falls on a weekend or holiday and your lab does not accept samples, contact ADEQ for a list of Arizona laboratories that accept weekend/holiday samples.

View chart of actions required based on routine and repeat sample results | View >