Mission Water Hardness & Quality Report (2026)

Mission's drinking water is managed by the District of Mission, drawing from the Hayward Lake Reservoir on the Stave River — a BC Hydro reservoir system in the mountains north of Mission — via the Mission Water Treatment Plant. Water is treated using coagulation, sedimentation, filtration, UV disinfection, and chloramination, meeting all Guidelines for Canadian Drinking Water Quality (GCDWQ) requirements. Hardness measures 80 mg/L (4.7 gpg) — classified as moderately hard by Health Canada, reflecting the Stave River watershed's moderate mineral content from the Fraser Valley and Cascade Mountain foothills terrain.

The Stave River watershed drains the Cascade Mountain Range and Fraser Valley foothills north of Mission — a geological landscape of Cretaceous granodiorite (Coast Mountain batholith fringe), Jurassic volcanic and sedimentary rock, and glaciofluvial sand and gravel deposits in the valley lowlands. While the upper Cascade Mountains contribute relatively soft water (like Metro Vancouver's sources), the Stave Valley's mixed geology — including some calcareous metasedimentary and volcaniclastic units in the Hayward Lake catchment — produces moderately elevated hardness compared to the ultra-soft Metro Vancouver mountain supply (4–6 mg/L). This explains Mission's 80 mg/L despite being in the same general Fraser Valley region as the very soft Abbotsford Metro Van supply zones.

At 80 mg/L, Mission residents experience moderate scale deposits on tap aerators and kettle elements — descaling every two months is advisable. Hot water tanks operate reliably at this hardness. The District of Mission provides water quality information at mission.ca; residents in older Downtown Mission buildings along the Fraser River waterfront should follow Health Canada lead precautionary guidance for pre-1960 properties.