Water Quality

COVID-19 Message

Flush water pipes before reopening buildings

Buildings that have been closed or have experienced significantly reduced water use should flush their internal pipes to replace the stagnant water with fresh water prior to occupants returning. Learn more about maintaining or restoring water quality in buildings.SPU corrects issue involving small amount of untreated water mixing with Cedar water supply

SPU corrects issue involving small amount of untreated water mixing with Cedar water supply

Seattle Public Utilities (SPU) has corrected an issue that may have caused a very small amount of untreated drinking water from the City's Lake Youngs reservoir to blend with treated drinking water. The amount of untreated water from the reservoir was likely less than 0.00002% of the water supply. The incident happened from December 17, 2020 to February 4, 2021 on the Cedar water supply, which provides water to about two-thirds of the region. The remaining one-third of the region's water supply is on a separate system (Tolt water supply) and was not impacted.

SPU's source water is among the best in the nation. Additionally, water in Lake Youngs is very well protected from pollution and routine tests show high quality. High levels of water treatment were provided upstream of the site and multiple daily water quality samples collected downstream of the site during the incident all had good results. For all these reasons, the risk to public health was extremely low during this time.

SPU reported the incident to the Washington State Department of Health which determined no public notice was required. However, to keep customers informed, we have posted this notice on the SPU website. For more information, including measures SPU is taking to prevent this from occurring again, please contact our drinking water quality engineers at (206) 615-0827 or drinkingwater.quality@seattle.gov.

Seattle Public Utilities (SPU) and its water quality laboratories strive to maintain the cleanest and best-tasting drinking water in the nation. The topics below cover SPU's procedures and what to do if you have concerns or issues with your water.

  • Cloudy water: Know when to report water that is discolored, foaming, or with gray sediment.
  • Water aesthetics: If your water doesn't come out of the tap tasting good and clean, there is usually something you can do about it at home.
  • Fluoride: SPU has supplied fluoridated drinking water to our customers since 1970.
  • Lead: Learn about lead and what you can do at home to lower your exposure to it from your drinking water.
  • Legionella: This bacteria can grow in building water systems and cause a very serious type of pneumonia.
  • Water Quality Lab: We have the largest state-accredited water utility laboratory, testing over 20,000 samples annually.
  • Backflow prevention and cross-connection control: Preserving the quality of our drinking water includes protecting the water as it passes through the pipes to all the buildings in the City.


Seattle's Drinking Water is Safe From COVID-19

Seattle's drinking water remains safe and protected against contaminants, including COVID-19 caused by the novel coronavirus.

The City's water is chlorinated to remove microbial contaminants, such as bacteria and viruses. The water is also treated to remove and inactivate microbial contaminants such as chlorine-resistant Cryptosporidium.

Additionally, Seattle Public Utilities (SPU) conducts water quality tests daily to help ensure contaminants stay out of our drinking water supply.

During emergency events, Seattle's drinking water facilities are considered high priority. This means essential services, like the delivery of water to customers, will be maintained as outlined in the utility's Continuity of Operations Plan.

The City of Seattle remains in close coordination with the Centers for Disease Control and Prevention, Washington State Department of Health (DOH) and Public Health - Seattle & King County and are following their guidelines in response to COVID-19.

Members of the public can call the DOH hotline at (800) 525-0127 and press # if they believe they have symptoms of COVID-19. Up-to-date information is also available on the Public Health - Seattle & King County's website.


Maintaining or Restoring Water Quality in Buildings

The COVID-19 pandemic has changed how water is used in commercial or industrial buildings that have closed or greatly reduced operations. Letting water sit in pipes for long periods of time can create water quality problems in these buildings. Buildings and businesses that have been closed or have significantly reduced water use should flush their internal pipes to replace the stagnant water with fresh water prior to occupants returning.

Seattle Public Utilities suggests following the recommendations from WA Department of Health's "COVID-19 Guidance for Legionella and Building Water System Closures," CDC guidelines, or the EPA's information.

Additional information from the WA DOH on building chlorination is available: "Shock Chlorination Guidance for Building Water Systems."