Kenmore Water Hardness & Quality Report (2026)

Kenmore, Washington, in King County at the northern tip of Lake Washington — a well-established King County community where the Sammamish River enters Lake Washington, known for the Kenmore Air seaplane base (the world's busiest seaplane port), the Burke-Gilman Trail, and easy access to the North King County recreational corridor — receives its municipal water from Seattle Public Utilities (SPU) or the Cascade Water Alliance, drawing from the Cedar River Watershed (Masonry Pool Reservoir) or the Tolt River reservoir system in the Cascade Range.

The soft 73.5 mg/L hardness and TDS of 188 mg/L reflect the Cascade Mountain supply's characteristically soft character. The Cedar River and Tolt River originate in the Western Cascade Range — draining Oligocene and Miocene andesitic and basaltic volcanic formations (the Ohanapecosh and Stevens Ridge volcanic sequences) and the Snoqualmie Batholith (Cretaceous granodiorite) — all non-carbonate, low-solubility igneous terrain. The SPU and Cascade Water Alliance treatment systems deliver this naturally soft Cascade supply throughout the Seattle metro north corridor. The slightly higher TDS (188 mg/L) compared to other Cascade Valley supplies reflects distribution system mineral inputs in the Lake Washington north corridor.

At 73.5 mg/L, Kenmore's water is soft — excellent for household appliances and comfortable for all uses. Scale forms slowly over many months, soap lathers well, and the dishwasher produces clean results. Semi-annual descaling of heating appliances is adequate. The PFAS level of 3.2 ppt is favorable for the north King County corridor — the Boeing facilities along the Lake Washington corridor and the northern Seattle suburban industrial zone contribute to the regional PFAS background, but the Cedar-Tolt supply's protected Cascade watershed provides a strong PFAS source water buffer.