Kent Water Hardness & Quality Report (2026)

Kent, Washington draws its municipal water supply through King County Water District No. 111 and the City of Kent Water Services department, sourcing from two primary origins: treated surface water from the Cedar River Watershed delivered through Seattle Public Utilities (SPU) and the Cascade Water Alliance regional distribution network; and groundwater from the Covington Wellfield and Clark Lake Aquifer — shallow wells tapping Pleistocene glacial outwash gravel beneath the valley floor in the Green–Duwamish River corridor of King County. Water hardness measures 74.5 mg/L — classified as moderately soft.

Kent's moderately soft supply reflects the combined character of Cedar River volcanic watershed water and Pleistocene glacial outwash groundwater of the Puget Lowland. Cedar River water originates from the Cascade Range — draining Miocene and Pliocene andesite, basalt, and volcanic tuff formations with minimal soluble carbonate content, producing inherently soft source water. The Covington wellfield draws from Fraser Glaciation–age outwash gravel (Vashon Stade glacial deposits) in the Green River Valley — sands and gravels derived from glacially eroded Precambrian–Tertiary Pacific Northwest materials that contain limited calcareous cement, contributing a modest but not major hardness addition to the supply.

With hardness at 74.5 mg/L, Kent residents experience light to moderate scale accumulation. Faucet aerators and showerheads develop deposits slowly — bi-monthly cleaning with citric acid solution is sufficient. Soap and shampoo lather well. Dishwashers produce clean glassware with light rinse-aid use. Hot water systems remain largely scale-free. King County Water District and City of Kent Water Services consistently deliver water meeting all Washington DOH and EPA Safe Drinking Water Act requirements.