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Water main flushing is a routine operation done to clean and maintain our water system. During this activity, water is forced through underground water mains and flushed out of fire hydrants to remove accumulated sediment. This flushing is done until the water coming from the hydrant runs clear. One section of water main is flushed at a time and can take from a few minutes to over an hour to complete. Flushing is important to maintain water quality as well as remove rust and sediment build-up in the pipes. While flushing water mains won’t entirely eliminate discolored water, it will help decrease it by removing some of the sediment and rust that has been resting in the pipes. Flushing helps reduce the level of discoloration and the time it takes for the water to clear when there’s a disturbance in the pipes.
Discolored water can happen when crews operate a fire hydrant, when there is a water main break or leak, or when the water in the pipes is forced to travel in a different direction than normal. When one of these events happens, naturally occurring sediment in the water and rust in the pipes get stirred up, causing the water to look discolored.
Yes. Every single day, SPU takes samples throughout the system of the drinking water that it provides to 1.4 million people. The water is tested for contaminants and is regulated by the Washington State Department of Health. Seattle’s water remains safe to drink.
Learn more about the West Seattle flushing process (pdf).