Boiling water is a widely used and effective method for eliminating many harmful microorganisms, making water safe for consumption. This process is particularly valuable when the quality of the water source is uncertain. Understanding how boiling works and its limitations ensures proper application for health protection.
The Science Behind Boiling Water
Boiling water makes it safe by using heat to disrupt the biological processes of microorganisms. As water reaches its boiling point, around 212°F (100°C) at sea level, the temperature causes irreversible damage to the structural components and proteins within bacteria, viruses, and protozoa. This process, known as denaturation, deactivates these microscopic organisms, preventing them from causing illness.
Denaturation, similar to how an egg white changes consistency when cooked, alters protein shape and function. This action destroys the cellular structures and genetic material of pathogens, rendering them non-viable. Boiling is effective against common waterborne pathogens like E. coli, Salmonella, Vibrio cholerae, Shigella, Hepatitis A, Rotavirus, Giardia lamblia cysts, and Cryptosporidium parvum oocysts.
What Boiling Doesn’t Remove
While boiling effectively eliminates biological contaminants, it does not remove all types of impurities. Chemical pollutants like pesticides, industrial chemicals, and nitrates remain in the water. Heavy metals such as lead, arsenic, and mercury are also not eliminated by boiling.
Boiling can even concentrate these non-biological contaminants. As water evaporates, the water volume decreases, leaving a more concentrated amount of dissolved chemical pollutants, heavy metals, or mineral salts. Sediment and dissolved solids also remain untouched.
How to Properly Boil Water
To properly boil water for drinking, begin by bringing clear water to a rolling boil. If the water appears cloudy or contains visible particulates, first filter it through a clean cloth, paper towel, or coffee filter, or allow sediment to settle before pouring off the clear water. Once the water reaches a rolling boil, maintain it for at least one minute.
For elevations above 6,500 feet (about 2,000 meters), boil the water for three minutes, as water boils at a lower temperature at higher altitudes. After boiling, allow the water to cool naturally without adding ice. Store it in clean, sanitized, and covered containers to prevent recontamination. The flat taste of boiled water can be improved by pouring it back and forth between two clean containers or by adding a small pinch of salt per quart.
When to Rely on Boiling Water
Boiling water is an effective method for biological decontamination when water quality is compromised. It is recommended during boil water advisories issued by local authorities, often due to microbiological contamination or threats like water main breaks or pressure loss.
Boiling is also a practical solution during emergencies, such as natural disasters, floods, or power outages that disrupt water treatment facilities. When traveling to areas with uncertain tap water quality or sourcing water from untreated natural sources, boiling provides an accessible way to make water safer to drink.