Emergency Drinking Water Treatment

During a natural disaster or emergency such as a boil water alert, public and private sources of drinking water may become unavailable or unsafe due to contamination. As a result, individuals may need to find an alternate drinking water source until the regular supply is restored and deemed safe for consumption.

Alternative Drinking Water Sources

There are several potential sources of water in emergency situations: Bottled water in factory-sealed containers. Melted ice cubes if made before the emergency occurred. However, don't attempt to freeze contaminated water, as freezing does not kill bacteria. Rainwater can be collected in clean, food grade storage containers; boil before drinking to kill bacteria. Water from the freshwater storage tank behind the toilet (not the bowl) can be used if boiled first. Don't use water from waterbeds or swimming pools as it may contain harmful chemicals or other impurities.

Methods of Purifying Water

There are several ways to purify water that may have been contaminated or come from a questionable source:

Boiling water - will destroy most bacteria, cysts and viruses. The US Centers for Disease Control and Prevention (CDC) recommends boiling drinking water for a minimum of 2 to 3 minutes at a good rolling boil.
Purification tablets - can usually be purchased from stores that sell camping supplies. Be sure to follow the directions on the package. Chemical disinfectants are generally effective against most forms of bacteria and viruses, but may not kill intestinal parasites (cysts), so boiling or filtering for cysts may still be needed.
Liquid (not granular) household bleach - should be free of additives or scents and contain a hypochlorite solution of at least 5.25%. The American Red Cross recommends adding 16 drops of bleach per gallon of water, letting the water stand for at least 30 minutes. If the water doesn't have a slight bleach odor, repeat the dosage and let stand another 15 minutes. A filter certified for chlorine reduction can be used to reduce to reduce excess chlorine.
Distillers – because water is boiled, they are effective at treating viruses, bacteria and cysts.
Filters and reverse osmosis units– can mechanically filter parasites if they have a cyst reduction claim, but most are not certified effective for viruses or bacteria.
Ultraviolet systems – could be used for disinfection of water provided the water hasn't been contaminated with wastewater, but like distillers, electricity would be needed to operate them. Also, the water supply must be clear in order for the UV light to be effective.

Tips for Storing an Emergency Water Supply

Families can purchase and store bottled water or bottle their own tap water to store in the event of an emergency.

Bottled water in factory-sealed containers can be stored indefinitely if kept in a proper environment.
If you choose to purify and store your own water, use glass or food grade plastic containers (i.e. PET) with screw-on caps. Clearly mark containers with the date the water was stored and replace annually (the old water can also be used for irrigation, toilet flushing or other non-potable water applications).
Don't store your emergency water supply in a garage, shed or other area where it could be exposed to heat or chemical fumes. Keep water containers high enough off the floor to limit exposure to flood waters.
Inspect your stored bottled water containers regularly for leaks or other problems. If you suspect the water quality has become compromised, discard the water or boil it before consuming.

For additional information, please visit Disaster Readiness Tips or contact NSF (info@nsf.org).