Frequent Questions

06. How do pathogens and indicators, like Total Coliforms, get into my drinking water?

When routine monitoring indicates that pathogen or indicator levels are in violation of a treatment technique or above a maximum contaminant level, your water supplier must take steps to improve treatment operations such as upgrading filtration or increasing disinfection to reduce pathogens levels and indicators so that the system returns to compliance. Water suppliers must inform their customers within the period of time specified in EPA’s Public Notification Rule as described below. Additional actions, such as providing alternative drinking water supplies or recommending that consumers boil their water prior to consumption, may be required to prevent serious risks to public health.

When must water suppliers notify their customers of a violation?
Pathogen or IndicatorPublic Notification Requirements
Cryptosporidium, Giardia lamblia, Legionella or viruses Water suppliers must notify their customers as soon as practical, but no later than 24 hours after the system learns of the violation.
Total coliforms When a non-acute/monthly MCL violation for total coliforms occurs (more than one total coliform-positive sample in a month for systems that take fewer than 40 samples/month; greater than 5.0% total coliform-positive samples for systems that take at least 40 samples/month), water suppliers must notify the state as soon as practical after the supplier learns of the violation and notify their customers no later than 30 days after the system learns of the violation.
Fecal coliform or E. coli When an acute MCL violation for total coliforms occurs (if a repeat sample tests positive for total coliform following a fecal coliform positive or E. coli positive routine sample or a repeat sample tests positive for fecal coliform or E. coli), water suppliers must notify the state and their customers as soon as practical, but no later than 24 hours after the system learns of the violation.  When a routine sample tests positive for fecal coliform or E. coli, water suppliers must notify the state within 24 hours, but public notification is not required because this is not an acute MCL violation. The water supplier must take steps to reduce the amount of fecal coliform or E. coli to meet the MCL. Also, when the water system fails to test for fecal coliform or E. coli when any repeat sample tests positive for total coliforms, water suppliers must notify customers as soon as practical, but no later than 24 hours after the system learns of the violation.
Turbidity When turbidity exceeds the maximum allowable limit (e.g., 1 NTU for conventional or direct filtration), water suppliers must notify the state within 24 hours. For violations of the 95th percentile limit (e.g., greater than 0.3 NTU for conventional or direct filtration), water suppliers must notify their customers as soon as practical, but no later than 30 days after the system learns of the violation.
Fecal indicators (Coliphage or Enterococci) Water suppliers must notify their customers as soon as practical, but no later than 30 days after the system learns of the violation.

If your water comes from a household well, check with your health department or local water systems that use ground water for information on contaminants of concern in your area.

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