You may notice a color change in your tap water following the flushing of the water main, during construction near your street and following a nearby water main break. The discoloration is normal and will last only a short time after the nearby hydrants have been flushed. When a hydrant is opened, the water in the mainline flows out at a high velocity. This creates a scouring action in the pipe which dislodges fine sediment particles that have accumulated in the pipe. The discoloration is due to suspended particles mixing with water that do not immediately settle.
During construction, frequent opening and closing of the gate valves leads to the same scouring action as during flushing. A significant amount of hydrant flushing occurs during construction and water main breaks, but some sediment usually ends up in water services too. There are no known health hazards associated with the discolored water.