A boil water notice (BWN) is a public health advisory issued by water authorities when the drinking water supply is suspected or confirmed to contain harmful microorganisms. This directive instructs consumers to boil all tap water before using it for consumption. The notice is a temporary, precautionary measure designed to prevent waterborne illnesses. It remains in effect until laboratory tests demonstrate the absence of contamination in the public water supply.
Why Public Health Officials Issue a Boil Water Notice
A BWN is typically triggered by events that compromise the physical integrity of the water system or by initial test results indicating a potential problem. A common cause is a sudden loss of water pressure in the distribution system. When pressure drops below 20 pounds per square inch, contaminants from the surrounding soil can be pulled into the water pipes through leaks or cracks.
Other physical disruptions, like water main breaks, power outages at treatment facilities, or natural disasters such as floods, can also lead to a notice. These events interrupt the normal disinfection process or introduce contaminants into the system. Officials also issue a BWN when laboratory analysis detects indicator bacteria, such as total coliforms or E. coli. This finding suggests that pathogens from sewage may have entered the water supply.
Mandatory Steps for Safe Water Use
The most immediate action during a BWN is to boil water intended for consumption. Water should be brought to a full, rolling boil and allowed to boil continuously for one full minute to kill potential protozoa, bacteria, and viruses. Once cooled, the water should be stored in a clean, covered container. Note that at elevations above 6,500 feet, the boiling time should be extended to three minutes due to the lower boiling point of water.
Boiled or bottled water must be used for all activities where water is consumed or could be ingested. Any ice made from tap water during the advisory period must be discarded, as freezing does not eliminate harmful microorganisms.
Activities Requiring Boiled Water
- Brushing teeth
- Making ice
- Preparing baby formula
- Washing produce
When preparing food, water must be boiled for at least one minute before being added to any dish or used to wash food preparation surfaces. For washing dishes by hand, a sanitizing rinse is necessary. This involves soaking cleaned dishes in a solution of one teaspoon of unscented household bleach per gallon of warm water for at least one minute. A dishwasher is acceptable if it has a sanitizing cycle or reaches a final rinse temperature of at least 150°F (66°C).
Bathing and showering are considered safe for healthy adults, provided no water is swallowed. Extra caution is advised for infants, young children, or those with compromised immune systems to prevent accidental ingestion. Pets should also be given cooled, boiled water or bottled water for drinking.
How a Boil Water Notice Is Lifted
A boil water notice cannot be lifted until the water system is completely restored and confirmed safe for consumption. The first step involves correcting the original problem, such as repairing a broken water main or restoring disinfectant levels. The affected water lines are then thoroughly flushed and disinfected to remove remaining contamination.
The resolution process relies on a strict testing protocol requiring water samples to be collected and analyzed by a certified laboratory. Water systems must collect a series of samples that show no presence of microbial contamination. In many cases, two consecutive sets of clean samples, often collected 24 hours apart, are required before the notice is officially rescinded.
Once laboratory results confirm the water is safe, the water authority issues an official notice to the public through the same channels used for the initial advisory. Even after the notice is lifted, consumers must take post-notice actions to flush their household plumbing. This involves running all cold water taps for a minimum of five minutes to clear out stagnant water from internal pipes.
Post-Notice Appliance Flushing
Appliances that use water must be addressed to ensure the entire system is running with newly confirmed safe water.
- Discard all ice made during the advisory and flush the ice maker’s water line by making and discarding several batches of new ice.
- Replace disposable water filters (in refrigerators, pitchers, or faucets), as they may have trapped contaminants.
- Cycle dishwashers and hot water heaters empty or flush them.