Vaudreuil-Dorion Water Hardness & Quality Report (2026)

Vaudreuil-Dorion's drinking water is managed by Ville de Vaudreuil-Dorion, a rapidly growing suburb at the far western tip of the Montreal metropolitan area where the Ottawa River meets the St. Lawrence River, drawing from the St. Lawrence River via the municipal water treatment plant. Water undergoes coagulation, sedimentation, filtration, UV disinfection, and chloramination, meeting all Guidelines for Canadian Drinking Water Quality (GCDWQ) requirements. Hardness measures 119.5 mg/L (7.0 gpg) — classified as moderately hard by Health Canada, near the upper boundary of the moderately hard range, reflecting the mixed carbonate character of the St. Lawrence supply at this western supply intake.

Vaudreuil-Dorion's 119.5 mg/L is notably harder than the typical Montreal Island boroughs (70–105 mg/L) and harder than the south shore Montérégie corridor (Saint-Constant 125 mg/L, Longueuil 73 mg/L from batch 8). The community sits at the confluence of the Ottawa River and St. Lawrence River — the Ottawa River at this point carries Precambrian Shield runoff from the upper Ottawa watershed that contributes additional dissolved minerals from Proterozoic limestone and dolostone in the Ottawa Valley, blending with the St. Lawrence supply to produce the elevated 119.5 mg/L reading at Vaudreuil-Dorion's intake.

At 119.5 mg/L, Vaudreuil-Dorion residents experience moderate scale deposits on kettle elements and tap aerators — descaling every six to eight weeks is adequate. Hot water tanks operate reliably at this hardness. Ville de Vaudreuil-Dorion publishes annual water quality reports following Ministère de l'Environnement standards. The municipality's rapid post-2000 residential growth has brought modern housing that meets current Health Canada plumbing standards.