Why do brewers need to remove chlorine from brewing water?

Brewers need to remove chlorine from brewing water primarily to avoid the development of unwanted flavors in the finished beer, specifically flavors associated with chlorophenols. Chlorine, when present in brewing water, can react with phenolic compounds during the brewing process to form chlorophenols, which impart off-flavors that are often described as medicinal or plastic-like. These undesirable flavors can significantly detract from the overall sensory experience of the beer and are highly regarded as faults in brewing.

In contrast, enhancing carbonation, increasing sweetness, and improving foam stability are not directly affected by the presence of chlorine in brewing water, which clearly highlights the importance of addressing chlorine for flavor quality in the final product.