Federal Way Water Hardness & Quality Report (2026)

Federal Way, Washington receives its drinking water from the Lakehaven Water & Sewer District. Approximately 60% of supply comes from the Regional Water Supply System (RWSS), formerly the Second Supply Project (SSP), sourcing surface water from the protected Green River watershed. Water is diverted below Howard Hanson Dam, treated at the Green River Filtration Facility, and delivered via a 34-mile pipeline in partnership with Tacoma, Kent, and Covington Water Districts. Additional supply includes groundwater from wells on the North Fork of the Green River within the same watershed. The district serves Federal Way and surrounding areas in South King County, ensuring compliance with federal and state standards through rigorous testing.

The Green River watershed originates in the Cascade Mountain foothills, characterized by granitic intrusions, volcanic basalts, and glacial deposits from the Pleistocene era. No major limestone aquifers are present, resulting in naturally soft water with low mineral content. The Cascade geology filters precipitation through forested slopes, minimizing mineral dissolution, while Howard Hanson Dam regulates flow without altering the soft water character. Wells tap shallow alluvial and glacial aquifers, adding minor hardness variability but maintaining an overall soft, low-mineralized supply.

As soft water, Federal Way's supply causes minimal scale buildup, protecting water heaters, dishwashers, and washing machines from limescale damage. Soap lathers easily, reducing usage and preventing dry skin or bathtub rings. No softener is needed or recommended; instead, monitor for corrosion risks in pipes due to low mineral content. Routine annual fixture checks are sufficient and scale-related repairs are rare. Third-party testing notes arsenic exceeding health guidelines from natural bedrock sources, though regulated levels comply; Lakehaven confirms full federal and state compliance.