A boil water notice is a public health advisory issued by local water authorities when the drinking water supply may be contaminated with disease-causing microorganisms, or pathogens. This precautionary measure instructs consumers to take specific steps to disinfect tap water before consumption to reduce the risk of waterborne illnesses caused by bacteria, viruses, or parasites.
Common Reasons Notices Are Issued
Water authorities issue these notices when conditions suggest potential contamination, even if pathogens have not been confirmed. A frequent cause is a loss of pressure in the water distribution system, often dropping below 20 pounds per square inch (psi). This pressure drop can allow groundwater or other contaminants to be drawn into the pipes through leaks.
Notices are also triggered by infrastructure failures, such as a water main break, which exposes the water supply. Power outages at treatment plants can disrupt the disinfection process, failing to eliminate microbes before distribution. A mandatory notice is also issued when routine testing confirms the presence of indicator organisms, such as E. coli or total coliform bacteria, signaling potential sewage contamination.
How to Safely Consume and Use Water
The most effective way to purify water during a notice is by boiling it, which reliably kills bacteria, viruses, and protozoa. Water should reach a full, rolling boil for at least one minute to destroy harmful germs. At elevations above 6,500 feet, boil the water for three minutes due to the lower boiling point.
After boiling, allow the water to cool before using it for drinking, making ice, or preparing food and beverages. This includes making baby formula, washing produce, and preparing coffee or tea. Discard any ice made with unboiled tap water.
Precautions are necessary for activities other than drinking. Brushing teeth requires using boiled and cooled, or bottled, water. Dishwashers are generally safe if they have a sanitizing cycle or reach a final rinse temperature of at least 150°F. When washing dishes by hand, rinse them in a solution of one teaspoon of unscented household bleach per gallon of warm water for at least one minute, then allow them to air dry completely.
Showering and bathing with tap water is generally safe, provided the water is not swallowed or allowed into the eyes or nose. However, infants, young children, or individuals with open wounds or compromised immune systems should use sponge baths or purified water to minimize exposure risk. Pets must also be given boiled or bottled water.
What Happens When the Notice Is Lifted
A boil water notice is only rescinded after water quality testing confirms the supply is safe for consumption. Authorities must collect multiple bacteriological samples from the distribution system over two consecutive days and receive negative results. This process ensures the problem is resolved and the water meets microbiological standards.
Once the notice is lifted, residents must flush their plumbing to clear any potentially contaminated water remaining in the pipes and appliances. This involves running all cold-water faucets for at least five minutes. Hot water heaters and lines should be flushed by running hot water for a minimum of 15 minutes (for a standard 40-gallon tank).
Appliance Maintenance
Appliance maintenance is also necessary. Discard all ice made during the notice and run the ice maker through a 24-hour cycle to flush the lines. Filters in water dispensers, refrigerators, and reverse osmosis systems should be replaced, as they may have trapped contaminants. Water softeners should be run through a regeneration cycle to ensure the system is clean.