Bacteria from sewage and animal wastes have presented the most frequent and immediate health risks to public water supplies over the years. The best and easiest way to test for the presence of harmful bacteria in drinking water is to determine the presence of coliform bacteria. Although the presence of coliform bacteria in drinking water is not necessarily harmful by itself, it is a good indication of the presence of fecal coliform bacteria and E. coli bacteria. Fecal coliforms and E. coli are particularly pathogenic strains of coliform bacteria. Their presence indicates that drinking water has been contaminated with sewage or animal (including human) wastes.

Does The Coliform Monitoring Rule Apply to Your Community?

Yes, all community public water systems as well as non-community water systems (public water system that does not serve a residential population) must submit samples on a monthly basis to an approved testing laboratory or the appropriate state agency for coliform bacteria testing. The samples are tested to determine their compliance with the maximum contaminant level (MCL) for total coliforms. Total coliform measurements include all strains of coliform bacteria. The MCL is the maximum permissible level of a contaminant in water that is delivered to any user of a public water system. Failure to submit samples, meet the MCL, or report sample results are all violations of the Safe Drinking Water Act.

Actions Your Community Should Be Taking

Your community must take all steps necessary to be sure that it does not exceed the MCL for coliform bacteria. The MCL is based on the presence or absence of total coliforms in a sample. Depending on the size of your community's drinking water system, you must submit between one and 50 routine samples per month to ensure that your system does not exceed the MCL. For example, if your community' s drinking water supply system serves between 8,501 and 12,900 people per month, then you are required to submit a minimum of 10 samples every month. For a system that submits 40 or more routine samples per month (those systems serving more than 33,000 people per month), if no more than 5.0 percent of the samples submitted during a month test positive for total coliforms the system would be in compliance with the MCL. For a system that submits less than 40 routine samples per month (those systems serving 33,000 people or less), the system would be in compliance if no more than one sample submitted during a month tests positive for total coliforms. In other words, a small water system may have one positive sample per month for total coliforms and still remain in compliance with the regulation.

Carefully follow procedures for sampling provided by your testing laboratory or the state agency. Routine samples are to be taken from taps used primarily for providing drinking water. However, samples are to be taken from different customer taps from month to month, for example, from kitchen or bathroom sink taps. Your state will work with you to establish a "sample-siting plan" for your community that lists where samples should be taken each month.

If your community's system does not test positive for total coliforms, you still must continue to submit the appropriate number of routine samples, review their results, report those results, and maintain a good operation and maintenance program for your water system. A good operation and maintenance program includes regular line flushing at fire hydrants and on dead ends.

If a sample does test positive for total coliforms, you must collect a specific number of repeat samples within 24 hours of the time you were notified of the result. For each routine sample that tests positive for total coliforms, you must collect three (3) repeat samples. For example, if two of your community' s routine samples test positive for total coliforms, then you must collect a total of six repeat samples. There is an exception for very small community drinking water systems (those serving only 25 to 1,000 people) who take only one routine sample per month. These small systems must collect four (4) repeat samples for each routine sample that tests positive for total coliforms.

These repeat samples must be collected within five service connections (or five household taps) of the original sample with at least one being at the original location, at least one upstream and at least one downstream. If total coliforms are detected in any repeat sample, your water system is deemed to be in violation of the MCL and you must notify the state agency no later than the end of the next business day after the day you learned of the violation. The problems that caused the contamination must be determined and corrected immediately. Contact one of the resource agencies listed in the back of this book if you need technical support or help in financing your actions. For certain small systems, an increase in the number of routine samples is required after a positive test for total coliforms. If your water system normally collects less than five routine samples per month and during a particular month collects at least one sample that tests positive for total coliforms, then your system will be required to collect at least five routine samples in the following month.

A violation of the total coliform MCL becomes "acute" if the fecal coliform or E. coli strains of coliform bacteria are identified in the total coliform samples taken during the same month in which your community's drinking water system tested positive for total coliforms. The presence of fecal coliform or E. coli in a sample causes a violation to become acute because it is evidence of sewage or animal waste contamination in your community's drinking water. Such contamination presents an urgent health problem. For acute violations, you must notify the state agency the same day you receive the results. For proper notification procedures, consult the "Public Notification" section of this Guide.

If your system collects less than five routine samples per month, a sanitary survey of your system is required at least every five years. This survey is usually done by the state agency, but may be performed by a state-approved agent. This survey is an on-site review of the water source, facilities, equipment, operation, and maintenance of a public water supply system designed to evaluate its ability to produce and distribute safe drinking water. An initial survey of all community public water systems that collect less than five routine samples per month was required to have been completed by June 29, 1994. The initial survey for non-community public water systems that collect less than five routine samples per month must be completed by June 29, 1999. After the sanitary survey is reviewed, the state has the authority to change the monitoring frequency for the public water supply system. This could reduce or increase the number of routine samples that are required to be taken each month.

Timetable

Your community has been required to test for total coliforms since 1975. The 1986 amendments to the Safe Drinking Water Act resulted in the publication of new rules that changed some of the procedures for testing, changed the MCL, and instituted certain public notification requirements related to coliform monitoring. These rules were published in final form on June 29, 1989, and became effective for all water systems on December 31, 1990.

Additional Information

The coliform monitoring requirements are published in Title 40 Code of Federal Regulations, Parts 141.21 & 141.63.
EPA and your state agency have several information sheets and pamphlets on sampling and testing for coliform bacteria. Contact your state agency for more information, or call the EPA Safe Drinking Water Hotline Telephone: 1/800/426-4791.
(See Resource Section for drinking water contacts)