Bothell Water Hardness & Quality Report (2026)

City of Bothell Water serves the city of Bothell, Washington, in King and Snohomish Counties, providing drinking water to approximately 15,423 residents. The utility purchases all of its surface water supply from the Cedar River Watershed and Tolt River Watershed, both managed by Seattle Public Utilities. Treatment takes place at the Cedar Treatment Plant and Tolt Treatment Plant, where coagulation, sedimentation, filtration, chlorination, and fluoridation are applied before distribution to homes and businesses throughout Bothell and surrounding communities in the service area.

The Puget Sound basin supplies Bothell through protected forested areas in the Cascade Mountains, where rainfall and snowmelt dominate. Pleistocene glacial deposits and sedimentary till shape the flow, with minimal interaction with limestone or heavy mineral strata. This surface-dominated hydrology produces very soft water, low in dissolved solids, due to rapid runoff over granitic and basaltic bedrock, in contrast to harder groundwater systems found in eastern Washington's aquifers.

Bothell's soft water minimises scale buildup in pipes and appliances, reducing maintenance needs for water heaters, dishwashers, and washing machines. Soap lathers efficiently, and skin feels less dry after showers. No water softener is required or recommended, as the low mineral content avoids efficiency losses; occasional descaling of fixtures suffices. Bothell earns an 'A' for legal compliance but a 'B' against health guidelines, with six contaminants — including 1,1-Dichloroethylene, Cobalt, and Uranium — exceeding advocacy thresholds; comprehensive filtration beyond standard municipal treatment is advised.