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Water Quality

Seattle Public Utilities (SPU) provides some of the highest quality drinking water in the nation because it comes from pristine, protected mountain sources: the Cedar River Watershed and South Fork Tolt River Watershed.

To ensure the safety of our drinking water, SPU’s water quality laboratory analyzes over 20,000 microbiological samples each year -- more than 50 a day -- and conducts chemical and physical monitoring daily, 365 days per year.

Each year, SPU publishes the Drinking Water Quality Report that summarizes water quality information for the year as required under the federal Safe Drinking Water Act. More detailed information can be found on the Water Quality Analyses page, which includes quarterly reports and annual summaries for dozens of drinking water quality parameters.

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.
  • 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.