Annual Hydrant Flushing

Each Spring, the City of Wilsonville conducts its annual water main flushing program. During this time, Utilities staff opens fire hydrants around the city and allow the water to flow through the pipes. This annual flushing verifies that hydrants and valves are in good operating condition in the event of an emergency. The hydrant flushing also flushes the minerals within the water will deposit within the pipes out of the water distribution system. Annual flushing for all public water systems is recommended by the American Water Works Association (AWWA).

Hydrant flushing is scheduled during the Spring prior to the peak water usage season. City staff will place signs in the general areas that they will be conducting flushing. Please note that due to the nature of the water distribution system, you may see the effects of the flushing in areas far removed from the actual work.  All flushing will occur between the hours of 9 AM and 3 PM.  Larger mains are flushed first, then crews move to smaller mains. The flushing route is carefully planned to control the direction of the water.  When a hydrant is opened, there may be temporary incidences of discolored water while fine sediment particles are flushed. There is no health hazards associated with the discolored water; the discoloration is caused by naturally occurring mineral deposits that form a thin film inside the pipe. This film is stirred up and removed during the flushing process. 

If you see crews flushing a hydrant in your street, avoid running tap water and using the washing machine or the dishwasher for at least 20-30 minutes after the crew departs, wait longer if you can. Waiting will reduce the chance that discolored water is drawn into your home plumbing system following the hydrant flush. If tap water is used during flushing, it could contain sediment from the lining of the water main.

Anyone who encounters discolored water should shut the water off and wait several minutes.  After waiting, check the clarity by running cold water for a few minutes, allowing new water to work its way into the pipes. In some cases, there may be slight discoloration for a few hours.

The discoloration only affects appearance; it does not affect the taste or quality. The water has been fully disinfected and is safe to drink. The mineral deposits that cause discoloration affect the aesthetics of the water only; they are not harmful to your health.

If after completing the above steps you are concerned about discolored water, please contact the Public Works Department at 503-682-4092.