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 water may come in contact with 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 American Water Works Association (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.
Most people can sense a chlorine residual around 1 mg/l. If your water smells strongly of chlorine, it is possible that your treatment facility conveys water over a long distance, requiring heavy chlorination to maintain chlorine residual throughout the system. (The chlorine residual also may be raised by treatment facilities during warm weather when chlorine dissipates readily from water.)
- Residual chlorine in your water is not harmful. It is actually required by the EPA (Environmental Protection Agency) and MassDEP in order to disinfect water before it is distributed to homes and offices.
- Boiling your tap water or chilling it in the refrigerator will remove the bleach smell from the water.
- The EPA and MassDEP requires chlorine in public water systems but recommends levels below 4mg/L. Chlorine can be smelled at levels of 1mg/L. The City of Methuen has a distribution residual ranging from 0.10 - 1.2mg/L depending on the distance from the treatment plant.
What Can You Do?
Fill a pitcher of water and set it aside for several hours while chlorine dissipates. Transferring the water rapidly between two pitchers can accelerate chlorine dissipation.
Do you have a question about your drinking water quality? If your home is served by our public water system, you should receive a link to Methuen’s consumer confidence report (CCR) each year by July 1 in your water bill. A CCR provides a general overview of the water quality delivered.