Dental Offices

Note: This information supersedes the “Issuing and Rescinding a Boil Water Advisory” portion of the Cryptosporidium and Water Handbook.

General Procedures

Reschedule appointments for immunocompromised patients, such as HIV-positive individuals, chemotherapy and transplant patients, and congenitally immunocompromised individuals.

Warn your patients before treatment that they are at greater risk for cryptosporidiosis if they are immunocompromised, and that they may wish to reschedule their treatment after the boil water advisory is lifted. Explain to all patients the current situation regarding water and indicate what procedures your office is following to protect their health.

Patients and employees should not use or consume water that has not been disinfected, or ice or drinks made from water that has not been disinfected.

Water should not be delivered to patients through the dental unit, ultrasonic scaler, or other dental equipment with water line connections to the public water system. Turn off the water supply to such equipment. Using disinfected water, flow water out of a bulb syringe when using high-speed hand pieces. This restriction does not apply if the water source is isolated from the municipal water system (e.g., a separate water reservoir or other water treatment device cleared for marketing by the Food and Drug Administration).

All employees with diarrheal illness should be regulated by standard rules of exclusion from work.

Drinking Water

For drinking water, use:

  • commercially-bottled water
  • and/or water that has been disinfected for Cryptosporidium by:
    • boiling at a rolling boil for 1 minute (at altitudes greater than 6,562 feet (>2,000 m), boil water for 3 minutes), or
    • distilling
  • and/or water hauled from an approved public water supply in a covered sanitized container
  • and/or water from a licensed drinking water hauler truck.

Note: Although chemicals (e.g., bleach) are sometimes used for disinfecting small volumes of drinking water for household use, chemical disinfection is generally not recommended for commercial establishments because of the lack of onsite equipment for testing chemical residuals. Furthermore, Cryptosporidium is poorly inactivated by chlorine or iodine disinfection. Cryptosporidium can be removed from water by filtering through a reverse osmosis filter, an “absolute one micron” filter, or a filter certified to remove Cryptosporidium under NSF International Standard #53 or #58 for either “cyst removal” or “cyst reduction.” (see A Guide to Water Filters for more information) However, unlike boiling or distilling, filtering as just described will not eliminate other potential disease-causing microorganisms, such as bacteria and viruses.


Please visit Infection Prevention and Control in Dental Settings—Hand Hygiene for more information.

Note: Cryptosporidium is not killed by alcohol gels and hand sanitizers.

When the Boil Water Advisory is Cancelled

  • Make sure dental units and other equipment with water line connections are flushed, cleaned, and sanitized according to manufacturer’s instructions.
  • Managers of large buildings with water-holding reservoirs should consult with their facility engineer and health department about draining the reservoir.
  • Flush pipes and faucets. Run cold water faucets continuously for at least 5 minutes.
  • Flush drinking fountains. Run water continuously for at least 5 minutes.
  • Run water softeners through a regeneration cycle.
  • Drain and refill hot water heaters set below 113°F.
  • Change all point-of-entry and point-of-use water filters, including those associated with equipment that uses water.