Boise Water Hardness & Quality Report (2026)

The City of Boise Public Works Department manages the water utility, serving approximately 230,000 residents across Ada County in the Treasure Valley region. Water sources include the Boise River for surface water and numerous groundwater wells tapping the Treasure Valley aquifer. Key treatment facilities include the River Treatment Plant, the GWTP (Groundwater Treatment Plant), and the proposed Three-Mile Creek Treatment Plant, with distribution covering the city of Boise and parts of unincorporated Ada County.

The Boise River watershed spans the Sawtooth Mountains, channeling snowmelt and precipitation through granitic and volcanic terrains before reaching the Treasure Valley. The Treasure Valley aquifer is a shallow unconfined system of Quaternary alluvial gravels, sands, and silts overlying Miocene basalt flows from the Columbia River Basalt Group. Limestone-rich soils and mineral-bearing alluvial deposits in the basin impart a hard character as dissolved calcium and magnesium accumulate during subsurface flow through these formations.

Scale buildup occurs in pipes, water heaters, and fixtures, reducing efficiency and lifespan. Water heaters suffer most, with mineral deposits increasing energy use by up to 30% and causing premature element failure. Increased soap consumption and poor lathering affect laundry, dishes, and bathing; regular deliming of appliances and flushing of heaters is advised. A water softener is recommended for comprehensive protection. Recent PFAS testing by the City of Boise shows levels below the EPA standard of four parts per trillion; treatment involves filtration, chlorine disinfection, and fluoridation at surface plants, while groundwater receives aeration and disinfection.