Chlorination
The most common method of disinfecting drinking water — adding chlorine or chloramine to kill bacteria, viruses, and parasites before water reaches your tap.
How It Works
Chlorination is one of the most important public health achievements of the 20th century, virtually eliminating waterborne diseases like cholera, typhoid, and dysentery in developed countries. Water systems use either free chlorine or chloramines (chlorine combined with ammonia). Chloramines produce fewer disinfection byproducts but are less effective at killing certain pathogens. The EPA requires water systems to maintain a disinfectant residual throughout the distribution system to prevent bacterial regrowth in pipes. Some consumers dislike the taste or smell of chlorine — activated carbon filters (including common pitcher filters like Brita) effectively remove chlorine and improve taste.
Related Terms
- Disinfection Byproducts (DBPs) — Chemical compounds formed when disinfectants (chlorine, chloramine) react with natural organic matter in water — including trihalomethanes (THMs) and haloacetic acids (HAAs), linked to cancer and reproductive issues.
- Surface Water — Water from rivers, lakes, and reservoirs — the drinking water source for the majority of large cities. Surface water requires more intensive treatment than groundwater because it is more exposed to contamination.
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About This Definition
This definition is part of the IsWaterSafe Drinking Water Safety Glossary — 22 terms explaining water contaminants, treatment methods, and safety standards. Written for homeowners, renters, journalists, and public health professionals.