Yakima Water Hardness & Quality Report (2026)

The City of Yakima Water Division serves approximately 97,000 residents across Yakima County, Washington, from West Valley to Terrace Heights. Primary water is sourced from the Naches River via an intake at its confluence with the Tieton River, about 6 miles west of the city, diverted through the Wapatox Canal by the Bureau of Reclamation to the Naches River Water Treatment Plant at Rowe Hill. Supplemental groundwater is drawn from four wells at Kiwanis Park, Kissel Park, Gardner Park, and Yakima Airport, all tapping the Ellensburg Aquifer. Treated water flows by gravity through a 48-inch pipeline to five covered reservoirs for distribution.

The Naches River drains the eastern Cascades within the Yakima River watershed, part of the Columbia River Basin, where snowmelt and rainfall percolate through volcanic and sedimentary terrains. Key formations include Miocene Columbia River Basalts and the Ellensburg Formation's sandstones and conglomerates, while the Ellensburg Aquifer — an unconfined alluvial aquifer of Quaternary valley-fill gravels — provides supplemental supply. Water dissolves calcium and magnesium from basaltic lavas and alluvial deposits, producing a moderately mineralised supply consistent with Cascade Range foothills basin hydrology.

At 28 mg/L, Yakima's water is classified as soft, causing minimal scale buildup on pipes, water heaters, and appliances; no softener is needed or recommended. Soap and detergents lather efficiently, and appliance lifespan is not shortened by mineral deposits. The 2024 City of Yakima Water Quality Report confirms compliance with EPA standards — TDS of 46 mg/L, sulfate at 3.46 mg/L, no lead or copper violations. Treatment at the Naches River Water Treatment Plant uses aluminum chlorohydrate (ACH) and polymer coagulation, anthracite/silica filtration (25 MGD capacity), and disinfection. Third-party analysis detects arsenic and chromium-6 above health guidelines; utility reports affirm overall safety.