Yes, the water coming from your sink typically contains chlorine or a chlorine-based compound. This presence is the direct result of disinfection, the final step in municipal water treatment. The chemical remains in the water as it travels through the distribution system to ensure it stays safe to drink right up to your tap and prevents the spread of waterborne diseases.
Why Chlorine is Added to Water Systems
The addition of chlorine to public water supplies is considered one of the most significant public health achievements of the last century. Before chlorination was widely adopted in the early 1900s, diseases like cholera and typhoid fever were common threats carried through contaminated water. Introducing this disinfectant drastically reduced the incidence of these waterborne illnesses.
Chlorine is added at the treatment plant to kill harmful microorganisms, including bacteria, viruses, and parasites. Once the water is treated, a small amount of the disinfectant, known as the chlorine residual, is intentionally left behind. This residual maintains continuous disinfection as the water flows through the distribution system.
The residual protects the water as it flows through miles of underground pipes to individual homes, safeguarding against potential contamination from leaks or breaks. The U.S. Environmental Protection Agency (EPA) requires water systems to maintain a detectable level of this residual. The EPA sets a maximum limit of 4 milligrams per liter (mg/L) for chlorine in drinking water. This level is considered safe for consumption while remaining effective enough to neutralize pathogens. Maintaining this residual concentration is a continuous balancing act for utilities, ensuring the water remains safe without causing unpleasant taste or odor.
Distinguishing Chlorine from Chloramines
The disinfectant found in your sink water is typically either free chlorine or chloramines, which are two distinct compounds used for the same purpose. Free chlorine refers to hypochlorous acid and hypochlorite ions, which are fast-acting, potent disinfectants. This form is particularly effective at quickly neutralizing pathogens at the treatment plant.
Free chlorine is volatile and tends to dissipate quickly, making it less effective for maintaining a residual over long distances. It also has a more noticeable, stronger odor and taste. When free chlorine reacts with organic material, it can form disinfection byproducts.
Chloramines are an alternative disinfectant created by combining chlorine with ammonia. This combination is a slower-acting but significantly more stable compound than free chlorine. Due to its greater stability, chloramine lasts much longer as it travels through pipes to the consumer’s tap.
Many utilities have switched to chloramine because it helps maintain better residual levels throughout extensive pipe networks and typically forms fewer disinfection byproducts. While chloramines contribute to the water’s taste, the odor is often less pronounced than that of free chlorine. However, chloramines are harder to remove at home due to their chemical stability.
Methods for Reducing Chlorine at Home
For individuals who wish to reduce the disinfectant levels in their tap water, several household methods are available, but their effectiveness depends on whether the water contains free chlorine or chloramines. For water treated with free chlorine, simply allowing it to sit in an open container for 24 hours will often lead to a reduction. Chlorine is a gas and will naturally evaporate into the air. Boiling water can significantly accelerate this process for free chlorine, as the increased temperature causes the compound to evaporate more rapidly. Neither simple standing nor boiling, however, is an effective method for removing the more stable chloramines.
The most reliable method for reducing both free chlorine and chloramines is filtration using carbon media. Standard activated carbon filters, such as those found in pitcher filters or refrigerator dispensers, are highly effective at removing free chlorine through a process called adsorption. The carbon binds the chlorine compounds, removing them from the water.
To remove chloramines, a more specialized form called catalytic carbon is typically required, especially in under-sink or whole-house systems. Catalytic carbon has a unique surface structure that not only adsorbs the compound but also promotes a chemical reaction to break the chloramine bond. This ensures comprehensive removal of both disinfectants, which also improves the water’s taste and odor.