Patient Guide

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Water Safety Guidelines

If your immune function is suppressed, follow these water safety guidelines and check with your local health department and utility to determine if your community’s tap water is safe for you to drink.

Tap Water

Water from your home faucet is considered safe if your water is from a city water supply or a municipal well serving highly populated areas.

Well Water

Examples of ways well water could become contaminated:

  • Construction is taking place near the well.
  • The well depth is shallow.
  • The well is located near a dairy or large numbers of livestock.
  • Flooding has recently occurred in the well area.

Municipal Wells

Drinking well water from municipal wells serving highly populated areas is considered safe because the water is tested for bacterial contamination more than twice a day.

Private Wells and Small Community Wells

Well water from private or small community wells is not considered safe for people who are immunosuppressed and at risk for infection unless it is tested daily and found to be negative for coliforms and Cryptosporidium organisms. It is recommended that other approved water sources be used instead, including boiled water or bottled water (see below).

Home Water-Filtration Devices

Common home water-filtration devices do not remove bacteria or viruses, so well-water treated only this way is not considered safe. If your well-water supply is chlorinated per guidelines provided by your local health department, then the chlorinated water treated in one or more of the following ways is considered safe to consume:

  • Reverse-osmosis treated
  • Distilled
  • Filtered through a filter with an absolute pore size of 1 micron or smaller  (NSF Standard #53 for cyst removal)

Safe Water Sources

The following sources of water are suggested if your water is not from a city water or municipal well supply:

  • Boiled water: At home, safe water can be made by bringing tap water to a rolling boil for one minute. After boiling, the water should be stored in a clean, covered container in the refrigerator. Discard water not used within 72 hours, or three days.
  • Distilled water: Water may be distilled using a steam distillation system. After distilling, the water should be stored in a clean, covered container in the refrigerator. Discard water not used within 72 hours, or three days.
  • Bottled water: Acceptable forms of bottled water are those that have been processed to remove organisms known to cause stomach or intestinal infection. Bottled water labels reading “well water,” “artesian well water,” “spring water,” or “mineral water” do not guarantee that the water is safe to drink. Bottled water labeled as having been treated in one or more of the following ways is considered safe: 
    • Reverse-osmosis treated
    • Distilled
    • Filtered through a filter with an absolute pore size of 1 micron or smaller (NSF Standard #53 for cyst removal)

To be sure that a specific brand of bottled water has undergone one of the above processes, contact the International Bottled Water Association (IBWA) at (800) 928-3711, or visit the IBWAwebsite. If the IBWA does not have information on a specific brand, call the bottling company directly. Members of the IBWA follow stricter manufacturing practices in their water bottling process than required by the U.S. Food and Drug Administration. Therefore, water bottled by a member of the IBWA may be preferable to other bottled water.

Water Filters

Most water-filtration devices will not make the water safe if the water supply has not been chlorinated. If you choose to install water filters on household water taps, purchase only filters certified by NSF International. The following specifications must also be met:

  • The filters must be designed to remove coliforms and Cryptosporidium. Any of the following types of filters are acceptable:
    • Reverse-osmosis filters
    • Filters with an absolute pore size of 1 micron or smaller
    • Filters tested and certified by NSF Standard #53 for cyst removal
  • The water-tap filter must be installed immediately before the water tap.
  • Manufacturer directions must be followed for filter maintenance and replacement.

Portable water filters (such as a Brita or Pur system) as well as refrigerator-dispensed water and ice machine systems do not meet filtration standards. Portable water systems filter out chemical impurities, not bacteria. If a portable water system (such as a Brita pitcher) is used in combination with a safe water supply (to improve water flavor and remove chlorine and other impurities), change the system’s filter frequently according to manufacturer’s guidelines.

For a list of approved filtration systems, call the National Sanitation Foundation International at (800) 673-8010 or search the NSF website for “Home Water Treatment Devices.”