FAQ: Why is drinking water chlorinated/chloraminated?
Drinking water is often chlorinated or chloraminated to kill microorganisms that could cause serious illnesses. Overall, chlorination of drinking water has benefited public health enormously.
There are other methods of disinfecting public drinking water, but they are often more expensive, and the potential health effects of using these other methods are generally less well understood. Additionally, some alternative disinfectants do not remain effective as the water is transported from the source to the tap through the distribution system.