A boil water advisory is a public health warning issued by local authorities when there is a known or potential risk that drinking water may be contaminated with disease-causing microorganisms. These advisories are typically initiated due to events that compromise the integrity of the water distribution system, such as a major water main break, a significant loss of pressure, or a failure at a water treatment plant. Contaminants of concern are usually biological, including bacteria like E. coli, viruses, and parasites such as Giardia and Cryptosporidium, which can cause gastrointestinal illness. Following the instructions provided by health officials during an advisory is important to protect against waterborne diseases.
Preparing Water for Consumption
The most reliable method for making tap water safe for drinking and food preparation is to bring it to a vigorous, rolling boil. This heat process is highly effective at neutralizing protozoa, bacteria, and viruses. To properly treat the water, it must reach a full rolling boil and maintain that state for at least one full minute. After boiling, the water should be allowed to cool naturally before being poured into a clean, covered container for storage.
For individuals residing at high elevations (above 6,500 feet), the boiling time needs to be extended. Because water boils at a lower temperature at increased altitudes, the water must be held at a rolling boil for a minimum of three minutes to ensure the destruction of all potential pathogens. Most household filters, including pitcher and refrigerator models, are not designed to remove bacteria and viruses, so all tap water, even if filtered, must still be boiled.
Bottled water is the simplest and safest alternative to boiling, as it is already certified for consumption. If boiling is not possible and bottled water is unavailable, unscented household liquid chlorine bleach can be used as a chemical disinfectant. For clear water, the standard recommendation is to add 8 drops of bleach per one gallon of water.
If the tap water appears cloudy, it should first be filtered through a clean cloth before disinfection, and the amount of bleach must be doubled to 16 drops, or about 1/4 teaspoon, per gallon. After mixing the bleach solution thoroughly, it must be allowed to stand for 30 minutes before it is considered safe for consumption. This chemically treated water should be stored in a clean, sanitized container with a cover until it is needed.
Safe Practices for Household Activities
Water used for personal hygiene and cleaning requires specific precautions to prevent accidental ingestion and contamination. When brushing teeth, untreated tap water should never be used; instead, use water that has been successfully boiled and cooled or use commercially bottled water. Similarly, any fruits and vegetables to be eaten raw must be washed using boiled and cooled water or bottled water.
Handwashing for general hygiene is typically safe with tap water and soap, but a rigorous technique is required, including scrubbing for 20 seconds and drying hands completely. If washing hands before preparing food, it is safer to use bottled or previously boiled water. For bathing and showering, adults can generally use tap water, but care must be taken to avoid swallowing any water or allowing it to enter the eyes, nose, or mouth.
Special caution is advised for infants, small children, and those with compromised immune systems, as they are more susceptible to waterborne pathogens. For these populations, a sponge bath using boiled or bottled water is recommended to eliminate the risk of accidental water ingestion. Water for pets should also be boiled and cooled before being placed in their dishes, as animals can be susceptible to the same contaminants as humans.
Washing dishes by hand requires a sanitizing step after the standard wash with hot, soapy water. After rinsing, dishes should be soaked for at least one minute in a separate basin containing a solution of one teaspoon of unscented household bleach per gallon of warm water. If using a dishwasher, it is safe only if the unit has a sanitizing cycle or if the final rinse temperature reaches at least 150 degrees Fahrenheit.
Restoring Normal Water Use
Once local health officials have announced that the advisory is lifted, several steps are necessary to clear the plumbing system of any untreated water. Begin by running all cold water faucets continuously for three to five minutes to flush the household pipes and fixtures. It is advisable to remove and clean the aerators (screens) from faucets before flushing, as sediment or bacteria may have collected there.
The hot water system also requires attention to ensure the water heater and lines are fully flushed. For a typical 40-gallon water tank, the hot water should be run for about 15 minutes, and for larger tanks, this time should be extended to 30 minutes or more. After the hot water lines are flushed, the dishwasher should be run empty through one cycle, preferably a hot or sanitize cycle, to clean the appliance.
Any ice made during the advisory period must be discarded, and the ice maker should be run through a full cycle, discarding the resulting ice for at least an hour to flush the internal water lines. Water filters, such as those in refrigerators or under-sink systems, must be replaced with new ones if water ran through them during the advisory, as the filters may have trapped contaminants. Appliances like coffee makers, humidifiers, and water dispensers should also be flushed, cleaned, and sanitized according to the manufacturer’s directions before resuming normal use.