Drinking Water - Washington Tracking Network (WTN)

Safe and reliable drinking water keeps us healthy. In Washington State, 88 percent of us get our water from public water systems.

Why is data about contaminants in drinking water important?

  • If present in drinking water, nitrate can impair our blood's ability to transport oxygen. Nitrate contamination of drinking water can come from the agricultural use of fertilizers and manure, septic tank and waste water effluent, and the disposal of animal wastes.
    • Less than 0.5% of our public water systems have reported nitrate levels above the federal limit of 10 mg/L.
  • If present in drinking water, synthetic organic compounds (SOCs) such as Atrazine and Di [2-ethylhexyl] phthalate (DEPH), and volatile organic compounds (VOCs) such as tetrachloroethene, also called perchloroethylene (PCE), and trichloroethylenes (TCE) can cause a long-term potential health risk.
    • In Washington State these compounds rarely occur in our drinking water and all community water systems that were tested met the standard.
  • Haloacetic acids (HAA5) are disinfection by-products (DBPs) formed when chlorine is used to disinfect water. HAA5 can vary seasonally and are generally tested every quarter on water systems where disinfection is necessary. If present in drinking water, DBPs can cause a long-term potential health risk.
    • About 0.8% of tested systems test above the maximum contaminant level of 60 µg/L.

View the Data

Drinking Water Data

Additional Resources

Drinking Water Program

Coliform Bacteria and Nitrates - Private Wells (PDF)

Drinking Water Publications

Private Wells: Information for Owners (PDF)

SENTRY Internet - Community Water System Information

Analysis of Contaminant Occurrence Data in Public Water Systems (Six Year Review) - EPA

National Report on Human Exposure to Environmental Chemicals - CDC

Radionuclides Rule for Drinking Water - EPA

Safe Drinking Water Act: Contaminants and MCLs

Safe Drinking Water Act - EPA

Water - CDC

Contact Us

For information or questions related to the Washington Tracking Network, email DOH.WTN@doh.wa.gov.

Let Us Know How You Used the Data

We love hearing about how our data is being used to make an impact on the health of Washingtonians. It also helps us to know what is meeting our users’ needs and how we can improve the information we provide. If you used our data, please tell us about it by sending an email to DOH.WTN@doh.wa.gov.

Would you like to receive updates?

Receive updates and information about WTN by joining our email newsletter.

Environmental Public Health Tracking logo