Water Quality

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.

Seattle's drinking water remains 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 1-800-525-0127 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 WA DOH on building chlorination is available: "Shock Chlorination Guidance for Building Water Systems."


Water Quality Topics

  • Cross-Connection Control – Protecting the quality of our drinking water includes protecting the water as it passes through the pipes to all the buildings in the City.
  • Lead – Learn about lead and what you can do at home to lower your exposure to it from your drinking water. 
  • Fluoride – SPU has supplied fluoridated drinking water to our customers since 1970.
  • Health and Water Quality Standards – Water quality standards are set to ensure your health is protected.
  • Cryptosporidium and Giardia – Find out about these microscopic organisms.
  • Legionella – This bacteria can grow in building water systems and cause a very serious type of pneumonia.
  • Water Taste, Odor and Color – Seattle has some of the finest tasting, purest source water in the world. But 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.
  • Algae and Filter Clogging – If you filter your water, during an algal bloom you may notice your filter clogs faster than usual. Typically, the blooms occur in the late spring, but they can occur at unexpected times of year. To help alleviate the filter clogging problem, you can install an inexpensive pre-filter.
  • Home Water Filters – Some customers filter their water to improve the things such as taste and odor while others filter their water because they are concerned about water safety. If you decide to filter your water at home, it is important to do it correctly and maintain your system regularly. NSF International evaluates and certifies filters.