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If your water just started smelling a bit like a swimming pool, it isn’t another mystery contaminant.

Along with the start of spring comes the annual cleaning of the water pipes in D.C., as well as Arlington County and the northeastern part of Fairfax County.

Washington Aqueduct, the organization responsible for treating and disinfecting the region’s drinking water, switches the disinfectant it uses from chloramine to chlorine between March 23 through May 2.

DC Water notes that “individuals may notice a slight change in the taste and smell of their drinking water” and recommends running cold water for two minutes, refrigerating tap water and using water filters to reduce the chlorine taste and smell.

For more information—of if you think there’s a bigger problem with your water (like a mysterious petroleum smell)—you can call DC Water at 202-612-3440.