A “Boil Water Order” or “Boil Water Advisory” is a public health notification issued when a community’s drinking water is or may be contaminated with disease-causing organisms. These advisories signal a potential threat from pathogens, including bacteria like E. coli, viruses, or parasites such as Giardia and Cryptosporidium. The contamination often follows events like water main breaks, floods, or a loss of system pressure, which may allow harmful microbes to enter the water supply. Understanding the public health guidelines for water purification is necessary for protecting personal and family health during the advisory period.
Exact Time and Technique for Purification
The standard instruction for purifying water under an advisory is to bring the water to a full, rolling boil. A rolling boil is defined by large, vigorous bubbles that continue to form even while stirring the water. Once this vigorous boiling is achieved, the water must be allowed to continue boiling for one full minute.
This minute of sustained heat is generally sufficient to neutralize waterborne pathogens at most elevations. After the boiling period, the water should be allowed to cool naturally before use. To ensure the purity of the treated water, it should be stored in clean, sanitized containers that are tightly covered to prevent recontamination.
A crucial adjustment is required for locations at high altitudes, typically defined as above 6,500 feet. At these elevations, water boils at a lower temperature because of reduced atmospheric pressure. The lower temperature means a longer exposure time is needed to achieve the same level of purification.
For those residing above 6,500 feet, the Centers for Disease Control and Prevention (CDC) recommends boiling the water for three full minutes once it reaches a rolling boil. If the water appears cloudy or contains visible sediment before boiling, it should first be filtered through a clean cloth or coffee filter to remove the larger particles.
How Boiling Eliminates Pathogens
Boiling water is widely regarded as the most reliable method for killing disease-causing organisms. This purification method functions by raising the water’s temperature to the thermal death point of common waterborne microbes. At sea level, water boils at 212°F (100°C), a temperature that rapidly destroys the structural integrity of most pathogens.
The high heat works by denaturing the proteins within the microbial cells, including bacteria, viruses, and parasitic cysts. This process involves altering the three-dimensional structure of the proteins, which renders the microorganisms inactive. The temperature achieved is enough to inactivate the specific pathogens that cause waterborne illnesses during a public water system advisory.
The requirement to boil for a sustained period, such as one minute at lower elevations, ensures that all water molecules within the pot reach the necessary temperature. The extended three-minute boiling time at high altitudes compensates for the lower maximum temperature the water can reach before it begins to vaporize. This extended exposure ensures the necessary cumulative heat dose is delivered to the microorganisms.
Essential Uses for Purified Water
During a boil water advisory, any water intended for internal consumption or contact with the mouth must be purified. This includes all drinking water, as well as the water used to prepare beverages like coffee, tea, and juice. Even if a coffee maker has an internal filter, the water should still be boiled and cooled before being added to the machine.
Boiled or bottled water must be used for making ice, and any ice made with unboiled tap water during the advisory should be discarded.
Food Preparation and Hygiene
Purified water is necessary for:
- Washing fruits and vegetables.
- Cooking and preparing baby formula or food. (If using formula, ready-to-use liquid formula is the safest choice.)
- Brushing teeth and rinsing the mouth.
- Providing water for pets.
For washing dishes by hand, a final rinse of the washed items should involve a solution made with disinfected water or a bleach rinse. Dishwashers can be used only if they have a sanitizing cycle that reaches a final rinse temperature of at least 150°F.
While showering and washing hands with tap water and soap is generally considered safe, caution must be exercised to avoid swallowing the water. Special consideration should be given to infants and individuals with compromised immune systems or open wounds, for whom it is safer to use purified water for bathing.