Tap water, also known as running water or municipal water, is supplied through a tap or a water dispenser valve and commonly used for drinking, cooking, and washing in many homes. While generally treated to meet safety standards, its quality can become uncertain. Boiling tap water is a widely recognized practice to address potential concerns about its safety for consumption, as it addresses certain types of contaminants.
The Primary Goal of Boiling
The fundamental purpose of boiling tap water is to enhance its safety for drinking by addressing potential biological contaminants. This process is commonly undertaken to make water potable, especially in scenarios such as emergencies or during boil water advisories issued by public health authorities. Such advisories are typically issued when there are concerns about harmful microorganisms entering the water supply, often due to events like water main breaks or system pressure loss.
Eliminating Microorganisms
Boiling water is an effective method for neutralizing many harmful biological agents, including bacteria, viruses, and parasites. The intense heat damages the structural components of these pathogens, such as their proteins and cell membranes, rendering them inactive and unable to reproduce. This process is more accurately described as pasteurization rather than sterilization, as it targets organisms that can cause harm to humans.
Common waterborne pathogens effectively inactivated by boiling include bacteria like Escherichia coli (E. coli), Salmonella, Vibrio cholera, and Shigella, along with viruses such as Hepatitis A and rotaviruses. Protozoa, including Giardia and Cryptosporidium, which are known for causing gastrointestinal illnesses, are also reliably eliminated. While some bacterial spores might survive boiling temperatures, these are typically not associated with waterborne diseases that pose a risk to human health through ingestion.
Substances That Remain
Despite its effectiveness against microorganisms, boiling water does not remove all contaminants. Chemical pollutants, heavy metals, and dissolved solids are unaffected by the boiling process. Substances like lead, arsenic, mercury, and fluoride have much higher boiling points than water or are heat-stable, meaning they do not evaporate or break down.
Pesticides, pharmaceuticals, and industrial chemicals also remain in the water after boiling. As water evaporates during boiling, these non-volatile contaminants can become more concentrated in the remaining water, potentially increasing their presence. Additionally, dissolved minerals like calcium and magnesium, which contribute to water hardness, remain and can even become more concentrated. Microplastics and sediments are also not removed by boiling, as they do not break down with heat.
Effective Boiling Practices
To ensure water is made safe through boiling, follow specific practices. First, bring the water to a full, rolling boil, where large, continuous bubbles are visible. For most locations at or near sea level, maintain this rolling boil for at least one minute to inactivate harmful microorganisms.
At altitudes above 6,500 feet (approximately 2,000 meters), water boils at a lower temperature, so the boiling time should be extended to three minutes to compensate for this difference. After boiling, allow the water to cool naturally before use. Once cooled, store the water in clean, sanitized containers with tight-fitting covers to prevent recontamination.