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Portland Water Bureau

From forest to faucet, we deliver the best drinking water in the world.


1120 SW Fifth Ave, Suite 600, Portland, OR 97204

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Unidirectional Flushing: Part of the Water Bureau’s System Maintenance & Water Quality Work

Unidirectional flushing maintains the water system.



The Portland Water Bureau will continue unidirectional flushing of water mains in the St. Johns and Cathedral Park neighborhoods. Flushing will occur between the Willamette River and Columbia Slough and from the railroad tracks to N. Bruce Avenue.

Flushing will be conducted between 9 a.m. and 3 p.m., Monday through Friday.

CLICK HERE to view a map of the current flushing area.


After completing unidirectional flushing of water mains in the St. Johns and Cathedral Park neighborhoods, the Water Bureau will begin conducting flushing of water mains in the following southeast Portland neighborhoods:

  • Powellhurst-Gilbert
  • Pleasant Valley/Powellhurst-Gilbert
  • Pleasant Valley

Flushing will occur between SE 111th Avenue on the west, SE 145th Avenue on east, SE Holgate Boulevard on the north, and SE Brookside Drive, SE 122nd Drive, and SE Blackberry Circle on the south.

Flushing will be conducted between 9 a.m. and 3 p.m., Monday through Friday.

CLICK HERE to view a map of the upcoming flushing area.

What is unidirectional flushing?

Drinking water systems, especially unfiltered systems like Portland, need to routinely clean the network of pipes to improve water quality. Over time, very fine sediment and organic matter from the Bull Run settle out of the water and accumulate in the bottom of the pipes. While the sediments are generally harmless, they can make the disinfectant in the water less effective. Additionally, sudden changes in the flow of water can disturb these sediments resulting in discolored water.

The Portland Water Bureau uses two techniques to clean and maintain the drinking water system: spot flushing and unidirectional flushing.

Spot flushing is used when a water quality problem has been identified. This includes when drinking water is discolored due to a disturbance in the system such as construction or other hydrant activity. Portland Water Bureau crews open fire hydrants to flush this water out of the system and bring fresh water into the pipes.

Unidirectional flushing is not used in response to a specific water quality issue but instead is used as routine maintenance to prevent problems from arising. The goal of unidirectional flushing is to scour and clean the insides of the water delivery pipes.  Cleaning the pipes removes sediment that build up in the pipes.  This reduces the potential for water quality problems.

Unidirectional flushing works by forcing water in the pipes to flow at much higher speeds than normal. Flushing crews first open and close valves to isolate sections of pipe, and then the water and any sediments in the pipes are flushed out through an open fire hydrant.

How does unidirectional flushing impact Portland Water Bureau customers?

Unidirectional flushing is used to improve and maintain our high-quality drinking water. Sediments and deposits in the pipes can discolor drinking water. The high speed water flows used in unidirectional flushing is an efficient and cost-effective way to remove sediments and deposits from the pipes and prevent potential water quality issues.

What to expect when flushing is happening in your neighborhood:

Unidirectional flushing will have minimal impacts to customers. If you see hydrant flushing crews working in the area, please drive carefully and treat them like any other road construction crew.

Flushing usually occurs Monday through Friday, between 9:00 a.m. and 3:00 p.m.

During flushing: Residents in the immediate vicinity of flushing may notice temporarily discolored water and lower than normal water pressure. The discoloration does not pose a health risk. However, avoid using tap water or running the washing machine or dishwasher until flushing is complete.

After flushing: If you experience some discoloration in your water, turn on each cold water faucet in your home and allow it to run for several minutes or until the water is clear.

If you experience ongoing water quality problems, call the Water Line: 503-823-7525 Monday through Friday, between 8:30 a.m. and 4:30 p.m.