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Quality Concerns

  • Winsome WilliamsWinsome Robinson Williams, Water Quality Analyst and Supervisor
    "The best part of my job is letting people know that our water is amazing."
  • SPU EngineersRyane Mar, an engineer for water-related Improvement Projects, with Daniel Huang, an engineer with the Dam Safety Program
    A lot of work goes into maintaining the region’s water supply. There are multiple types and ages of water mains, Seattle’s geography is challenging with lakes and hills, and the number of federal and state regulations that SPU has to meet is substantial.
  • Alex ChenAlex Chen, Senior Water Quality Engineer
    "I see myself as an advocate for our customers. Together with other water quality engineers, I ensure that our water protects public health, meets requirements, and tastes and smells great."
More information about your water.

The Details About Our Water Sources and Their Potential Contaminants

To ensure tap water is safe to drink, the Environmental Protection Agency and the Washington State Board of Health regulate the amount of certain contaminants in water provided by public water systems. The U.S. Food and Drug Administration and the Washington State Department of Agriculture regulations establish limits for contaminants in bottled water that must provide the same protection for public health.

Washington’s Source Water Assessment Program is conducted by the Department of Health (DOH) Office of Drinking Water. According to DOH, all surface waters are given a susceptibility rating of “high,” regardless of whether contaminants have been detected or whether there are any sources of contaminants in the watershed. Information on the source water assessments is available from the DOH website.

Sources of drinking water (both tap water and bottled water) include rivers, lakes, streams, ponds, reservoirs, springs, and wells. As water travels over the surface of the land or through the ground, it dissolves naturally occurring minerals and, in some cases, radioactive material, and can pick up substances resulting from the presence of animals or from human activity.

Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of contaminants does not necessarily indicate that water poses a health risk. More information about contaminants and potential health effects can be obtained by calling the Environmental Protection Agency’s Safe Drinking Water Hotline at (800) 426-4791.

In Seattle’s surface water supplies, the potential sources of contamination include:

  • microbial contaminants, such as viruses, bacteria, and protozoa from wildlife;
  • inorganic contaminants, such as salts and metals, which are naturally occurring; and
  • organic contaminants, which result from chlorine combining with the naturally occurring organic matter.

Some people may be more vulnerable to contaminants in drinking water than the general population. Immuno-compromised persons such as persons with cancer undergoing chemotherapy, persons who have undergone organ transplants, people with HIV/AIDS or other immune system disorders, some elderly, and infants can be particularly at risk from infections. These people should seek advice about drinking water from their health care providers. Environmental Protection Agency/Centers for Disease Control guidelines on appropriate means to lessen the risk of infection by Cryptosporidium and other microbial contaminants are available from the Safe Drinking Water Hotline at (800) 426-4791.