Frequently Asked Questions - Water Supply & Water Quality

Where does the District get its water supply?

The District primarily gets its water supply from groundwater wells located throughout the District. The District is also connected to the regional water system (operated by Seattle Public Utilities) through a contract maintained by the Cascade Water Alliance.
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Does the District add anything to my water?

The District has been adding chlorine to the groundwater supply for many years to treat aesthetic problems such as taste and odor issues and currently chlorinates the water for disinfection purposes. Surface water sources, such as the water received from the regional system from the Tolt and Cedar River watersheds, are required by state and federal law to be treated for disinfection, and chlorine is added to the surface water supply. Fluoride is added to match levels found in the regional water supply to promote dental health.
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Is the District's water hard or soft?

Water from the District’s groundwater supply is considered medium hard, and water from the regional water supply is soft. Water hardness refers to the amount of dissolved minerals in the water, primarily calcium and magnesium in the case of hard water, and sodium for treated soft water.
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How often is my water tested?

In accordance with federal and state regulations, the water in each of our wells throughout the distribution system is tested once every three years. Over 700 samples are taken annually. The Washington Department of Health (DOH) allows us to monitor for some contaminants less than once per year because the concentrations of these contaminants do not change frequently. Water is collected and sent to independent testing laboratories and all test results are reported to DOH. The District’s water meets all federal and state standards.
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How can I learn more about my drinking water quality?

Please review our Annual Drinking Water Reports here.
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Where does my wastewater go?

Wastewater flows to different areas depending on which facilities you have on your property. Approximately half of our customers are connected to the regional wastewater treatment system. Water that flows into the sewage system is send to the King County South Treatment Plant where it undergoes several treatment processes before being released through an outfall pipe into Puget Sound. The rest of our customers utilize septic systems, which is an onsite treatment system where wastewater is recycled on the same property where it originates. In a well functioning septic system, the waste is purified and returned to the groundwater. It is essential to maintain your septic system for maximum operational benefits.
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