A Boil Water Advisory (BWA) is a public health notification issued by water authorities when the drinking water supply is compromised. This precautionary measure protects residents from illness caused by waterborne pathogens. The advisory instructs the community to boil tap water before consumption until water quality is confirmed safe. It remains in effect until public health officials confirm that any risk of contamination has been eliminated.
What Triggers a Boil Water Advisory
Advisories are commonly issued following a failure in the water distribution system that allows contaminants to enter the pipes. One frequent trigger is a water main break, which causes a drop in system pressure below 20 pounds per square inch (psi). This loss of pressure allows untreated groundwater or soil to be drawn into the water lines.
A BWA may also be initiated when routine testing detects harmful microorganisms, such as E. coli, bacteria, viruses, or parasites. Flooding, power outages at treatment plants, or other natural disasters can also compromise the integrity of the water treatment process. When contamination is suspected, an advisory is issued immediately to safeguard public health.
Safe Water Use During the Advisory
The primary action during a BWA is to make all water used for consumption safe by bringing it to a full, rolling boil. Water should be kept at a rolling boil for at least one minute to effectively kill disease-causing organisms like protozoa, bacteria, and viruses. At altitudes above 6,500 feet, where water boils at a lower temperature, the boiling time should be extended to three minutes.
Boiled and cooled water, or bottled water, must be used for daily activities:
- Drinking
- Preparing all food and beverages
- Making ice
- Preparing infant formula
- Washing fruits and vegetables
- Brushing teeth
Hand-washing dishes requires a final sanitizing step: soaking them in a solution of one teaspoon of unscented household bleach per gallon of water for at least one minute before air-drying. Dishwashers are safe only if they have a hot wash cycle reaching 150°F or a sanitizing cycle. For bathing and showering, the water is generally safe for healthy adults, but avoid swallowing the water. Infants, toddlers, and individuals with compromised immune systems should use sponge baths with pre-boiled or bottled water.
Lifting the Advisory
A Boil Water Advisory is concluded only after utility officials confirm the water supply is safe for consumption. Confirmation involves collecting multiple water samples across the distribution system over time. These samples are tested for the absence of indicator organisms, such as total coliforms or E. coli. The utility must receive at least two consecutive sets of clear test results, typically taken 24 hours apart, before the advisory is officially lifted.
Post-Advisory Flushing Steps
Once the “all clear” notification is issued, homeowners must flush their internal plumbing.
- Run all cold water faucets for at least five minutes to clear the pipes.
- To flush a hot water tank, run the hot water faucet for 15 minutes (40-gallon tank) or up to 30 minutes (larger tanks).
- Discard all ice made during the advisory period and run the ice maker through a 24-hour cycle, discarding the first three batches of new ice.
- Replace any water filters, such as those in refrigerators or point-of-use reverse osmosis systems, to ensure no residual contamination remains.