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Bacterial Contamination of Drinking Water at Public Facilities

Facilities that serve water to the public sometimes have elevated chlorine and bacteria levels in their treated drinking water, and additional actions are needed. This fact sheet provides public facilities with information about how to protect their customers’ health during an advisory situation.

Emergency Chlorination Notice

An Emergency Chlorination Notice means that at this point your water is safe, but as a precautionary measure, any ice and premixed beverages (i.e. juice, lemonade, formula, etc.) made prior to the notice being issued should be discarded.

Boil Water Advisory

Health effects Associated with Bacteria in Water

Coliform bacteria act as a signal that other microbes which may cause illness are present in the water. Typical symptoms may include diarrhea, cramps, nausea, or yellowing of eyes and skin (jaundice) with headaches or fatigue. Note that these symptoms may be caused by factors other than unsafe water. If people develop symptoms during a boil water notice, they should contact their local health department or health care provider right away.

General Advice for All Public Facilities

  • Inform the public (staff, students and patients) by posting the DNR notice (available from local DNR offices) at faucets and in other prominent locations instructing the public not to drink the water or use it for mixing baby formula.
  • Turn off drinking fountains.
  • Dump ice if it was made on-site, purchase ice from a safe source, clean and sanitize ice machines after “all clear” has been issued.
  • Provide SAFE water for drinking and preparing food, juice, other beverages, and ice. Examples of safe water include:
    • Commercially bottled water.
    • Packaged ice from an approved source.
    • Water that has been at a rolling boil for 1 minute (source: CDC–Centers for Disease Control). Although boiling will make water safe, we recommend that public facilities use a commercial source of safe water.
    • A public water supply system that is safe. Any transport container, whether it is a gallon jug or a tanker truck, must be washed and sanitized before filling with safe, clean water. Sanitize by immersing for 1 minute in a solution of 1 teaspoon of chlorine bleach (5.25%, unscented) per gallon of clean water.

Hospitals, Dental and other Health Care Facilities

  • Follow the section on General Advice for all Public Facilities.

  • All health care facilities should use sterile water for flushing wounds, bottled water for surgical scrub, tube feeding, washing newborns, etc.

  • Dentists and dental hygienists should discontinue use of water cooled instruments such as high-speed handpieces, air/water syringes, and cavitrons; substitute bottled water applied with a bulb syringe for cooling and rinsing purposes; use rubber dams as appropriate; defer treatment for patients who may be at risk, such as small children, the elderly, and those with chronic diseases or suppressed immune systems.


  •  Follow the section on General Advice for All Public Facilities.

  • Post signs in guest rooms that instruct the public not to drink water or use it for brushing teeth, making baby formula, or bathing infants.

Food Service, Food Preparation Facilities

  • Follow the section on General Advice for All Public Facilities.

  • Use only commercially bottled water for ingestion; washing ready to eat foods such as fruit and vegetables; making coffee; cooking; and reconstituting juices, carbonated beverages or other drinks.

  • Turn off all post-mix beverage machines and dump premixed beverages on hand such as juice, lemonade, coffee, soda, ice tea, etc.

  • Turn off beverage vending machines that use the contaminated water supply.

  • Wash utensils either manually or with a dishwasher. Be sure the final rinse of the dishes is done with the proper strength of sanitizer, a bleach solution (one tablespoon of bleach in 2 gallons of cool water) or using 180-degree water.

  • Thoroughly wash hands as usual. Wear gloves after hand washing and prior to handling ready to eat foods.

These procedures must remain in effect until the municipality issues the “all clear” or your private well tests safe. After you are notified that the water is safe and prior to use, clean and sanitize the ice machine, beverage machines and any other piece of equipment that uses tap water.

Follow-up Sampling and Cleaning of Wells (for facilities on a private well)

  • Work with your well contractor to investigate and clean the water system.
  • Work with your local DNR representative to collect necessary follow-up samples.

Municipal Water Users

Resume normal use of the water when you are notified by your system official.

For More Information

Last revised November 21, 2018