Hydrant Flushing

Hydrant Flushing and Maintenance Program

The Fire Department, working with the Public Works – Operations, maintains approximately 1,600 hydrants throughout the city (2,065 in the Fire Department’s service area, which includes the Riverdale, Alto Park and Rivergrove districts).

Maintenance involves:

  • Checking for visible leaks
  • Testing water pressure, flow and operation
  • Charging the hydrant to allow air to escape and the barrel of the hydrant to be filled with water
  • Making sure that the hydrant drains properly so that it will not have water in the barrel during freezing weather
  • Checking to make sure caps and valves are in working order
  • Clearing any brush or vegetation from around the hydrant
  • Repairing any broken or problem hydrants

While all hydrants are maintained, some hydrants are also flushed. Not every hydrant needs to be flushed, only the hydrants located at the end of a waterline (dead-end hydrants). This routine maintenance is necessary to maintain the integrity of the water system and continue to deliver the highest quality water possible to customers.

Hydrant flushing - what happens?

During this program, the City will be using fire hydrants to discharge a large volume of water from the water system – essentially, flushing the water system.

Why flush fire hydrants?

  1. To clean water lines
  2. To ensure that they are working properly

By discharging a large volume of water through a fire hydrant, water flow within the pipeline is increased. This increased flow actually scours the inside of the pipeline, removing and then transporting silt and mineral deposits out of the water system. In addition, this process provides Lake Oswego with the opportunity to assess the general condition of the hydrant and test for flow and operations.

Will Hydrant Flushing Affect Your Water?

During the flushing process, you may experience some water discoloration, especially when work is being done in your immediate neighborhood. As water is flushed through water lines and out the hydrant, silt and mineral sediment can cause water to become discolored. Once the hydrant flushing is complete, the water quality will return to normal.

Can I drink from the tap during hydrant flushing?

Although the water may not be visually appealing, it is safe to drink and continues to meet all federal and state drinking water standards. There is no health hazard associated with the discolored water.

How long does hydrant flushing take?

Fire hydrant flushing typically takes 15 minutes to several hours, but discolored water may last up to 4 hours.

Flushing releases a large amount of chlorinated water, will this chlorinated water get into the waterways?

No. The City will use a dechlorinator when the hydrant flushing is performed.

What should you do?

Here’s what you should do if hydrant flushing is taking place in your neighborhood:

  1. If possible, avoid using water while the hydrant flushing is taking place. By not taking water from the tap or running appliances that use water (dishwashers and washing machines), you can prevent discolored water from entering your household plumbing altogether.
  2. Don’t do laundry while hydrant flushing is taking place. The discolored water can sometimes stain fabrics. Wait until water runs clear at the tap before using your washing machine, and wash a load of dark clothes first.
  3. If you encounter discolored water following hydrant flushing, run the cold water taps throughout your home (bathroom sinks and tubs, kitchen faucets, etc.) for 5 to 10 minutes or until water clears. This allows discolored water to work its way out of your household plumbing.
  4. If, after hydrant flushing, your water pressure or volume seems low, clean faucet screens to remove silt and mineral sediment that could be obstructing water flow.

More information.

For questions regarding the hydrant flushing program or if you experience water quality problems lasting more than four hours following hydrant flushing, contact the Public Works – Water Operations at 503-635-0280.

Find the closest hydrant

The City has an interactive map available to search for information including hydrants and water lines.


City of Lake Oswego Oregon fire hydrant flushing
City of Lake Oswego Oregon fire hydrant flushing
City of Lake Oswego Oregon water line flushing
City of Lake Oswego Oregon water line flushing