Chomedey Water Hardness & Quality Report (2026)

Chomedey (the largest district of Ville de Laval, located on the west of Laval island) receives its drinking water through Ville de Laval, drawing from the Rivière des Prairies — the northern channel separating Laval island from the Laurentian mainland — via the Laval Water Treatment Plant. Water is treated using coagulation, sedimentation, ozonation, filtration, UV disinfection, and chloramination, fully meeting the Guidelines for Canadian Drinking Water Quality (GCDWQ). Hardness measures 77.5 mg/L (4.5 gpg) — classified as moderately hard by Health Canada, consistent with the Rivière des Prairies' blended Shield and lowlands chemistry.

The Rivière des Prairies draws from the Ottawa River system, carrying a blend of soft Precambrian Shield inflows from the Laurentian Highlands and moderately harder water from the St. Lawrence Lowlands Ordovician limestone plain. Chomedey's distribution zone on the west Laval island receives supply from the Rivière des Prairies intake where Shield tributary dilution is notable — producing a supply moderately softer than the primary St. Lawrence. The river traverses Ordovician Trenton Group limestone and dolostone formations of the lowland plain, contributing moderate dissolved calcium.

At 77.5 mg/L, Chomedey residents see only light scale deposits in kettles and on tap aerators — descaling every two to three months is adequate. Hot water tanks perform reliably at this hardness. Ville de Laval notes that Chomedey's dense post-war residential housing and newer suburban developments span several decades — residents in older properties should consult Health Canada guidance on lead and enquire about lead service line status with Ville de Laval, which has an active replacement programme underway.