Many people wonder if their tap water needs extra treatment before drinking. While public water systems often deliver safe water, certain situations require additional precautions. Knowing when and how to purify water helps ensure its safety.
Scenarios Requiring Boiling
Boiling tap water is recommended in several situations to ensure its safety. Public health authorities issue “boil water advisories” when the water supply is compromised. These advisories typically follow events like water main breaks, pressure loss in the distribution system, or confirmed contamination, which can allow harmful microorganisms to enter the supply.
During emergencies or natural disasters, such as floods or power outages, water infrastructure can be damaged, leading to contamination. Floodwaters, for example, can introduce sewage or chemicals into water systems. In these instances, tap water may not be safe for drinking, washing dishes, brushing teeth, or preparing food.
Individuals traveling to areas with less reliable water treatment or using untreated sources should also consider boiling. Certain populations are more susceptible to waterborne pathogens. Infants, the elderly, and those with compromised immune systems face a higher risk of illness from contaminated water, making boiling a protective step.
How Boiling Purifies Water
Boiling effectively purifies water by eliminating many harmful microorganisms through heat. High temperatures damage the structural components and disrupt essential life processes of bacteria, viruses, and protozoa. This process inactivates or kills pathogens like _Giardia_, _Cryptosporidium_, _E. coli_, _Salmonella_, and viruses such as Hepatitis A.
Many waterborne microorganisms are inactivated at temperatures well below the boiling point. For example, _Cryptosporidium_ oocysts become non-infectious in less than a minute at temperatures exceeding 70°C. A rolling boil ensures the water reaches a temperature sufficient to destroy these disease-causing agents, making the water microbiologically safe to drink.
However, boiling does not remove all impurities. It is ineffective against heavy metals like lead, arsenic, and mercury, and chemicals such as fluoride, nitrates, pesticides, and pharmaceuticals. Boiling also does not eliminate sediment or microplastics. In some cases, as water evaporates, it can concentrate non-volatile contaminants, potentially increasing their levels.
Steps for Boiling Water
Boiling water properly involves a few straightforward steps. If water appears cloudy or contains visible particles, first filter it through a clean cloth, paper towel, or coffee filter, or allow it to settle. This initial step removes larger debris that boiling cannot eliminate.
Next, bring the clear water to a full, rolling boil, meaning it bubbles rapidly and continuously. At sea level, maintain this rolling boil for at least one minute to kill most disease-causing organisms. For elevations above 6,500 feet (approximately 2,000 meters), boil the water for a minimum of three minutes, as water boils at a lower temperature.
After boiling, allow the water to cool naturally before consumption. Do not add ice to cool it quickly, as this could reintroduce contaminants. Store the cooled, boiled water in clean, sanitized containers with tight-fitting covers to prevent recontamination. Boiled water can be used for drinking, cooking, brushing teeth, making ice, and washing food.
Other Water Purification Methods and Safe Tap Water
Other water purification methods exist for emergencies or when boiling is not practical.
Chemical Disinfection
Chemical disinfection involves adding household bleach or iodine tablets to water. Unscented household bleach (5.25% or 8.25% sodium hypochlorite) requires a few drops per gallon, followed by a waiting period. Iodine tablets are also available per product instructions. These methods are effective against many bacteria and viruses but may not eliminate all protozoa, like _Cryptosporidium_, or chemical contaminants.
Portable Filters
Portable water filters, designed for emergency use, can remove particles and some microorganisms. Their effectiveness varies depending on the filter’s pore size and design.
In areas with well-regulated public water systems, tap water is generally safe to drink without boiling. The U.S. Environmental Protection Agency (EPA) sets drinking water quality standards. Public water systems continuously monitor and treat water to meet these guidelines, ensuring it is free from harmful contaminant levels.
Despite these assurances, water quality concerns can arise from aging infrastructure or localized issues. Consumers can access local water quality reports, called Consumer Confidence Reports (CCRs), provided annually by their water supplier. These reports detail the water’s source, detected contaminants, and compliance with safety standards, informing individuals about local water quality.