Redmond Water Hardness & Quality Report (2026)

Redmond, Washington, in King County at the eastern end of Lake Washington — a global technology hub, headquarters of Microsoft and Nintendo of America, and the 'Bicycle Capital of the Northwest' — draws its municipal water supply from the Cedar River Watershed (Chester Morse Lake) and South Fork Tolt River (Tolt Reservoir) via Seattle Public Utilities (SPU), distributed to Redmond through the Cascade Water Alliance regional system. Water hardness in Redmond measures 24.5 mg/L — classified as extremely soft, one of the softest municipal water supplies in the United States.

Redmond's extraordinary softness reflects the Cedar River and South Fork Tolt River Cascade Range watershed geology. Both watersheds originate on the western slopes of the Cascade Range near Snoqualmie Pass — draining the Columbia River Basalt Group (Miocene basalt flows — calcium-poor mafic volcanic rock), Eocene North Cascades crystalline terrain, and the Snoqualmie Batholith (Oligocene granodiorite — calcium-poor). The cool, wet Pacific Northwest Cascade climate produces extremely high rainfall that flows rapidly off the calcium-poor volcanic and crystalline bedrock with minimal mineral residence time. The result is extraordinarily soft water — one of the lowest hardness supplies of any large US metropolitan water system.

With hardness at 24.5 mg/L, Redmond residents experience essentially no scale challenges. Seattle Public Utilities and Cascade Water Alliance consistently deliver water meeting all Washington DOE and EPA Safe Drinking Water Act requirements.