Yakima Water Hardness & Quality Report (2026)

Yakima, Washington, the Yakima County seat in the Yakima Valley of central Washington, draws its municipal water supply from the Naches River (a Yakima River tributary) via the City of Yakima Water Division, with the primary intake on the Naches River above the city in Yakima County. The Naches River drains the eastern Cascade Range in Kittitas and Yakima Counties — high-elevation Cascade Range volcanic terrain west of the Yakima Valley. Water hardness measures 46.5 mg/L — classified as very soft, exceptionally soft for an eastern Washington city in an arid basin.

Yakima's very soft supply reflects the dominance of Cascade Range volcanic source water in the Naches River. The Naches River headwaters on American River drain: the Ohanapecosh Formation volcanic sequences (Oligocene–Miocene lavas, tuffs, and breccia); Columbia River Basalt Group flows of the eastern Cascades; and the Miocene–Pliocene Ellensburg Formation fluvial volcanic debris. These Cascade Range volcanic formations — basalt, andesite, rhyolite, and volcaniclastic tuff — are essentially free of soluble calcium carbonate. The Naches delivers soft Cascade snowmelt to Yakima even as the broader Yakima Valley environment is semi-arid, because the supply originates in the high-elevation, wet Cascade crest zone.

With hardness at 46.5 mg/L, Yakima residents enjoy very soft water with minimal scale challenges in household use. Faucet aerators and showerheads rarely need descaling. Soap lathers well. Dishwashers produce clean glassware. City of Yakima Water Division consistently delivers water meeting all Washington DOH and EPA Safe Drinking Water Act requirements.