Water held unused in building pipes while businesses or activities are shut down or have unused floors or sections becomes stagnant. Conditions may develop increasing the risk for the growth and spread of waterborne bacteria, such as Legionella or biofilm, in the building piping. Disinfectant in the water, such as chlorine, will likely dissipate or become undetectable.
Actions are necessary to ensure the water in the building is safe as well as taste and odor free before resumption of normal water use. The Center for Disease Control CDC) has very detailed information on reactivating plumbing systems after dormant conditions on its website at: https://www.cdc.gov/coronavirus/2019-ncov/php/building-water-system.html.