Building Flushing Guidance

Before reaching customer’s taps, water is drawn out of the upper Tualatin River, then thoroughly treated at the Joint Water Commission Water Treatment Plant to remove particles, viruses, bacteria, and other organisms from the drinking water, including COVID-19. Learn more about how this water treatment process keeps drinking water safe.

However, when water sits for too long in the plumbing systems of vacant or low use buildings, it can become stagnate and may cause water quality problems and health risks.

What can building owners or managers to keep water safe?

To ensure safe water and protect public health, the Oregon Health Authority advises following these four steps to flush building plumbing before resuming regular building use:

  1. Flush one area and fixture at a time, starting in the basement and working up to other floors.
  2. Remove aerators and flush cold water first, then hot water.
  3. Set the hot water heater to at least 120 degrees Fahrenheit.
  4. Collect one or more coliform bacteria samples after flushing and have the samples analyzed by a local water testing lab.

Remember, each building is unique and will require different actions to protect water quality during idle periods or before reopening.



  • Call: 503-615-6702
  • Email
  • Mail: Joint Water Commission, 150 East Main Street, Third Floor, Hillsboro, OR 97123