Chlorine is added to public water supplies as a disinfectant to eliminate harmful bacteria and viruses, a practice that has drastically improved public health. Once the water reaches the home, many people choose to remove the residual chlorine because of its distinct taste, odor, and potential effects in specific applications. Removing chlorine is achievable through several different methods, ranging from simple, low-cost techniques to comprehensive filtration systems.
Understanding Free Chlorine Versus Chloramines
Selecting a removal method requires understanding the specific disinfectant present in the local water supply. Treatment facilities typically use one of two forms: free chlorine or chloramines. Free chlorine is the most reactive form, consisting of hypochlorous acid and hypochlorite ions that actively neutralize contaminants.
Free chlorine is a highly effective, fast-acting disinfectant, but it dissipates quickly as it travels through the distribution network. Because it is highly reactive, it can combine with organic matter to form disinfection byproducts.
To maintain a longer-lasting residual disinfectant across vast water systems, many utilities have switched to chloramines, formed by combining chlorine with ammonia. This creates a more stable compound, primarily monochloramine, that remains active longer in the pipes. The increased stability of chloramines means they are more difficult to remove than free chlorine, affecting the efficiency of many common removal methods.
Immediate and Low-Cost Removal Techniques
For removing chlorine from small volumes of water without installing a system, simple physical and chemical processes offer immediate solutions. The most accessible physical method is aeration, or letting the water sit exposed to the air. Free chlorine is a volatile gas that naturally escapes from the water’s surface over time.
This passive method, known as aging, requires the water to be left uncovered in an open container for 24 to 48 hours for the free chlorine to dissipate. Increasing the water’s surface area, such as using a wide-mouthed pitcher, speeds up the process.
Boiling water accelerates evaporation, as the heat quickly converts the volatile free chlorine into a gas. A rolling boil maintained for 15 to 20 minutes can reduce the free chlorine content, though this method is only practical for small batches.
Neither aeration nor boiling is effective for removing chloramines due to their greater chemical stability. For a rapid solution for both chlorine and chloramines, chemical neutralization is necessary. Adding Vitamin C (ascorbic acid or sodium ascorbate) neutralizes the disinfectants through a quick chemical reaction. This redox reaction converts the chlorine and chloramines into harmless chloride ions, making it an excellent method for treating bathwater or emergency water supplies.
Filtration and System-Based Removal
For consistent, high-volume chlorine and chloramine removal, physical filtration systems are the most reliable long-term choice. Activated carbon filtration is the industry standard, working through adsorption where the porous carbon media traps contaminants. Standard Granular Activated Carbon (GAC) is highly effective for free chlorine, as the carbon both adsorbs the chlorine and catalyzes a reaction that converts it into chloride.
Chloramine removal is more demanding and requires a specialized media known as catalytic carbon. Catalytic carbon has a modified surface that accelerates the reaction needed to break the stable chlorine-ammonia bond. Because chloramine is more persistent, the filter media must have a longer contact time with the water for efficient neutralization.
These filtration systems are installed in two primary configurations: Point-of-Use (POU) and Point-of-Entry (POE).
Point-of-Use (POU)
POU systems, such as pitcher filters or under-sink units, treat water only at a single tap, making them ideal for drinking and cooking water.
Point-of-Entry (POE)
POE systems, commonly known as whole-house filters, are installed where the main water line enters the home. This ensures all water used for showering, bathing, and appliances is treated.
Reverse Osmosis (RO) systems are also highly effective at removing disinfectants, though the membrane itself does not accomplish the removal. The RO process works very slowly, necessitating the use of a pre-carbon filter to remove chlorine and chloramines before the water reaches the semi-permeable membrane. This pre-filtration step is essential because both chlorine and chloramines will permanently damage the delicate RO membrane. The slow flow rate provides extended contact time, making the carbon stage efficient at treating stable chloramine compounds.
Specific Applications for Chlorine-Free Water
The need for chlorine removal extends beyond taste and odor, becoming necessary in several sensitive environments. In aquatic environments, chlorine and chloramines are highly toxic to fish and other aquatic life because the chemical is designed to destroy cell walls. The only way to safely introduce tap water to an aquarium is by treating it with a chemical dechlorinator, which typically contains sodium thiosulfate or a similar compound to instantly neutralize the disinfectant.
For gardening and hydroponics, the concern is the impact of disinfectants on beneficial microbial communities in the soil. While chlorinated water can kill microorganisms in the top layer of soil, populations usually rebound quickly, and chlorine binds to soil particles, preventing deeper penetration. For sensitive plants or hydroponic systems where beneficial microbes are artificially maintained, aging the water or using a specialized whole-house filter is recommended to protect the microbial balance.
Many individuals seek to remove chlorine from their bath and shower water to reduce skin and respiratory irritation. During a hot shower, the chlorine volatilizes rapidly, and the resulting chlorine gas can be inhaled, causing respiratory discomfort. This physical off-gassing and the drying effect of chlorine on the skin and hair can be mitigated by using a Vitamin C shower filter or installing a POE system that treats all incoming water.