Tap water frequently contains chlorine, added to eliminate harmful microorganisms like bacteria and viruses. This disinfection process makes water safe for consumption and prevents waterborne diseases. Many individuals wonder if a common household practice, boiling, can effectively remove this chlorine from their drinking water.
How Boiling Removes Chlorine
Boiling water can reduce the amount of free chlorine present in tap water. Chlorine is a volatile substance, readily changing from liquid to gas. Its boiling point is around -34°C, far below water’s 100°C. As water heats up, chlorine molecules begin to escape into the air through a process called volatilization.
For effective removal of free chlorine, a vigorous rolling boil is recommended for about 15 to 20 minutes. Effectiveness depends on factors like initial chlorine concentration, water volume, and container surface area. A wider pot, for instance, allows faster evaporation. However, boiling is not effective at removing chloramines, which are more stable compounds formed from chlorine and ammonia, used as disinfectants due to their longer-lasting properties. Chloramines do not evaporate easily with heat, so they remain in the water even after boiling.
What Boiling Does Not Remove
While boiling eliminates most biological contaminants like bacteria, viruses, and parasites, it does not remove many chemical pollutants. Boiling is ineffective against non-volatile substances like heavy metals (lead, mercury, arsenic). These elements have higher boiling points than water and remain in the liquid.
Boiling does not remove nitrates, pesticides, pharmaceuticals, or dissolved solids. As water evaporates during boiling, the concentration of these non-volatile contaminants can increase in the remaining water. Relying solely on boiling for water purification can leave behind numerous potentially harmful chemicals.
Other Ways to Remove Chlorine
Several other methods can effectively remove chlorine from water. Activated carbon filters are a common option, found in pitcher filters, faucet attachments, and whole-house filtration systems. These filters work by adsorbing chlorine molecules onto the surface of the carbon. Activated carbon filters can remove a substantial percentage of chlorine.
Chemical treatments, such as adding ascorbic acid (Vitamin C) or sodium ascorbate, can neutralize both chlorine and chloramines. This method is used for specific purposes, like dechlorinating water for aquariums or medical procedures. Allowing water to sit out in an open container for several hours to a day can reduce free chlorine levels through natural evaporation, though this process is slower and less effective for chloramines. Distillation involves boiling water and collecting the condensed steam, leaving most contaminants, including chlorine, behind.