Coquitlam Water Hardness & Quality Report (2026)

Coquitlam receives its drinking water through Metro Vancouver (Greater Vancouver Water District — GVWD), sourced from three protected mountain watersheds including the Coquitlam Reservoir — the largest of Metro Vancouver's three primary supply reservoirs, located in the mountains above Coquitlam's Westwood Plateau — along with Capilano and Seymour reservoirs on the North Shore. Water is treated at the Coquitlam Water Treatment Plant and Seymour-Capilano Filtration Plant using UV disinfection, ozonation, biofiltration, and chloramination, fully meeting all Guidelines for Canadian Drinking Water Quality (GCDWQ) requirements. Hardness is just 4 mg/L (0.2 gpg) — exceptionally soft.

The Coquitlam Reservoir sits within the Coast Mountains on granite, diorite, and volcanic rock of the Cascade Belt and Coast Crystalline Complex — highly resistant igneous and metamorphic geology that releases virtually no dissolved calcium or magnesium to rainfall and snowmelt. Coquitlam has the geographic distinction of hosting one of its own primary supply reservoirs in the mountains directly above the city — a proximity advantage that minimises distribution travel time from source to tap. The protected watershed status ensures pristine, ultra-low-mineral supply year-round.

Coquitlam homes enjoy effectively scale-free water — taps, showerheads, and appliances remain free of mineral deposits indefinitely. Kettles do not require descaling. However, the very low mineral content makes the water naturally aggressive toward metal plumbing — older Coquitlam homes with galvanised or copper pipes may experience pinhole corrosion over time. Metro Vancouver conditions the water with lime to reduce corrosivity, but residents in pre-1980 homes should consider having their tap water tested and may benefit from a pH-stabilising inline filter as a precautionary measure.