A Boil Water Advisory (BWA) is a public health notification issued by local authorities when the drinking water supply is or may become contaminated with harmful microorganisms. This notice serves as a precautionary measure to prevent illness from waterborne pathogens. It instructs the public to treat their tap water before consuming it until testing confirms the water system is safe.
Why Authorities Issue the Advisory
Advisories are often triggered by events that compromise the physical integrity of the water distribution system, creating a pathway for external contamination. A sudden and unexpected drop in water pressure, for instance, can allow untreated groundwater to infiltrate pipes through cracks or leaks. For example, a pressure drop below 20 pounds per square inch is a common benchmark for concern.
Large-scale infrastructure failures, such as a water main break or a power outage at a treatment facility, also frequently prompt a BWA. These incidents can disrupt the disinfection process or introduce foreign materials into the supply. Furthermore, authorities issue an advisory if routine testing detects the presence of microbiological indicators of sewage contamination, such as E. coli.
High turbidity, or cloudiness, in the water is another common cause because suspended particles can shield pathogens from standard chemical disinfectants like chlorine. This particulate matter makes water treatment less effective, prompting the advisory as a proactive step to ensure public safety.
Essential Steps for Safe Water Use
The most direct way to eliminate pathogens during an advisory is to heat the water to a high temperature. To properly treat water, bring it to a full, rolling boil for a minimum of one minute. This duration is sufficient to kill common waterborne germs, including those that can survive chemical disinfection, such as Giardia and Cryptosporidium.
After boiling, allow the water to cool naturally before storing it in a clean, covered container. For those living at altitudes above 6,500 feet, the boiling time should be extended to three minutes due to the lower boiling point of water. Home filtration systems, including pitchers and refrigerator filters, do not remove bacteria or viruses and should not be relied upon as a substitute for boiling.
You must use boiled or commercially bottled water for all internal consumption activities. This includes drinking, preparing food, making ice, and mixing baby formula. Any ice made with unboiled tap water before or during the advisory should be thrown out.
Even brushing your teeth must be done using water that has been boiled and cooled or with bottled water. When washing dishes by hand, wash and rinse them as usual with hot water, then soak them for at least one minute in a sanitizing solution. This solution can be made by adding one teaspoon of unscented household liquid bleach to every gallon of warm water.
For activities like showering and bathing, tap water is generally safe, provided you take care not to swallow any water. It is advisable to give young children and infants sponge baths to minimize any accidental ingestion. Laundry is also safe to do as usual, and hot water from the tap can be used for shaving.
Pets should also be given boiled and cooled water for drinking, as they can be susceptible to the same waterborne illnesses as humans.
How an Advisory is Lifted
A Boil Water Advisory remains in effect until public health officials confirm the water quality has been restored to safety standards. To lift the advisory, the water utility must collect multiple samples over a period of time, often at least 48 hours, and have them tested at a certified laboratory. These tests must consistently show the absence of harmful bacteria or other contaminants.
Once the advisory is officially rescinded, consumers must take several steps to clear their home plumbing of any residual untreated water. First, you should run all cold-water faucets for a minimum of five minutes to flush the lines. Next, flush the hot water lines for at least 15 minutes for a standard 40-gallon hot water tank.
Appliances that use tap water must also be addressed to ensure complete safety. You should discard all ice from automatic ice makers and run the machine through a 24-hour cycle, throwing out the first three batches of ice. Water filters, such as those in refrigerators or pitcher systems, must be removed and replaced, as they may have trapped contaminants.