Water Quality

Smells Like Chlorine


The chlorine odor of tap water can be traced to the chlorine “residual,” a low level of chlorine maintained in water to guard against bacteria, viruses and parasites, which may be in water as it flows from the treatment plant to points of use. In the US, even treatment plants that use non-chlorine disinfection technologies are required to add chlorine to the water before it flows into the distribution system. The chlorine residual acts like a “body guard” for water in transit. As long as there is a residual level of chlorine, the consumer is reasonably protected from harmful microorganisms.

According to the AWWA, if the chlorine residual level is sufficient without being excessive, water will not smell like chlorine. Yet, sensitivity to the odor of chlorine varies among consumers. The US Environmental Protection Agency (EPA) requires treatment facilities to maintain a chlorine residual level that is chemically detectable but no greater than 4 mg/l. Four milligrams per liter is the “Maximum Residual Disinfectant Level” for chlorine, and it is the level below which there are no known or expected risks to health from exposure to the disinfectant.