A boil water advisory is a public health directive instructing consumers to boil tap water before using it for consumption. This precautionary measure is put in place when there is a known or potential risk that disease-causing microorganisms, such as bacteria, viruses, or parasites, have entered the public water supply. Boiling water neutralizes these biological threats, making the water safe for consumption and food preparation. The advisory serves as a temporary safeguard until water quality can be confirmed as meeting all safety standards.
Understanding the Triggers for an Advisory
Advisories are issued following an event that compromises the physical integrity or biological safety of the water distribution system. The most common trigger is an infrastructure failure resulting in a sudden loss of water pressure within the pipes. Pressure drops, often falling below 20 pounds per square inch, can occur due to water main breaks, equipment malfunctions, or power outages at pumping stations. When pressure is lost, it creates a vacuum that allows groundwater and surrounding contaminants to seep into the pipes through cracks or leaks.
Another reason for an advisory is the confirmed detection of harmful microorganisms like E. coli, Giardia, or Cryptosporidium during routine water quality testing. These pathogens indicate sewage contamination and pose a direct risk of causing gastrointestinal illness. When tests show confirmed contamination, the advisory is mandatory and alerts the public to an immediate health threat.
Many advisories are issued as precautionary measures when contamination is high but not yet confirmed. This often happens after major natural disasters like floods, which can overwhelm water treatment facilities and distribution lines with surface runoff. Advisories may also follow a fire near water lines or a system shutdown for repair, where the possibility of intrusion is significant. In these cases, the alert is a proactive step to protect the public while laboratory testing is underway.
How to Safely Use Water
The primary action during an advisory is to bring water to a full, rolling boil for at least one minute to destroy potential pathogens. Once boiled, the water must be allowed to cool completely before it is used for drinking, preparing food, or brushing teeth. For people living at elevations above 6,500 feet, where water boils at a lower temperature, the boiling time should be extended to three minutes to ensure adequate disinfection.
All water intended for consumption must be boiled or replaced with bottled water, including water used to prepare beverages like coffee, tea, and infant formula. Boiled or bottled water should be used to wash food items, such as fresh fruits and vegetables, that will not be cooked. Ice made with unboiled tap water must be discarded, and ice makers should be turned off.
For personal hygiene, only boiled and cooled water or bottled water should be used for brushing teeth. Hand washing with soap and unboiled tap water is considered safe, but a bottled or boiled water rinse is advised before preparing food. When washing dishes by hand, they should be rinsed for at least one minute in a mixture of one teaspoon of unscented household bleach per gallon of water, or run through a dishwasher with a high-temperature sanitizing cycle.
Showering and bathing with unboiled tap water is safe for healthy adults, provided no water is swallowed and care is taken to avoid getting it in the eyes or nose. Infants and young children should be sponge-bathed to prevent accidental ingestion. People with open wounds or compromised immune systems may consider using bottled or boiled water for personal washing. Pets should also be given boiled and cooled water, as they are susceptible to the same waterborne illnesses.
The Process of Rescinding an Advisory
A boil water advisory is not lifted until water quality tests confirm the elimination of the microbial threat. Utility officials must first correct the underlying problem, such as repairing a broken main or restoring system pressure, before beginning the testing process. The advisory remains in effect until a minimum of two consecutive sets of water samples, collected from the affected area at least 24 hours apart, show no presence of coliform bacteria.
These bacteriological tests take time, meaning most advisories last a minimum of 48 to 72 hours from the time the problem is corrected. The public must wait for an official “all clear” notification from the water utility or local government before resuming normal tap water use.
Once the advisory is officially rescinded, consumers should take steps to flush their plumbing systems. This involves running all cold water faucets for three to five minutes to clear the pipes of any stagnant or contaminated water. Automatic ice makers should be flushed by making and discarding three batches of ice, and water filters in refrigerators or pitchers should be replaced.