Rimouski Water Hardness & Quality Report (2026)

Rimouski's drinking water is managed by Ville de Rimouski, the regional capital of the Bas-Saint-Laurent, drawing from the Rivière Rimouski via the municipal water treatment plant in the river valley. Water undergoes coagulation, sedimentation, filtration, UV disinfection, and chloramination, fully meeting the Guidelines for Canadian Drinking Water Quality (GCDWQ). Hardness measures just 16 mg/L (0.9 gpg) — classified as soft by Health Canada, among the lowest values of any major Quebec city, reflecting the Rivière Rimouski's characteristically mineral-free drainage from the Appalachian highlands of the southern Quebec hinterland.

The Rivière Rimouski drains the Appalachian Highlands (Chic-Choc Mountains foothills and Laurentian fringe) of the Bas-Saint-Laurent — a landscape of ancient Cambrian and Ordovician metasedimentary and volcanic rocks of the Gaspé–Appalachian terrane, and locally the fringe of the Precambrian Shield to the north. These resistant rock types — including metamorphic slate, phyllite, quartzite, and Precambrian gneiss — dissolve very little calcium or magnesium, producing the exceptionally soft, clear water characteristic of Rimouski and the broader Bas-Saint-Laurent region. Chicoutimi (11.5 mg/L) and Rimouski (16 mg/L) represent Quebec's softest major municipal supplies.

With 16 mg/L of hardness, Rimouski homes are completely free from scale build-up — kettles, taps, and showerheads remain clear without any descaling maintenance. Hot water tanks have a near-unlimited operational lifespan from a scale perspective. The very soft, slightly acidic water is mildly corrosive — older Rimouski homes with original copper or galvanised pipes benefit from periodic plumbing checks. Ville de Rimouski publishes annual water quality reports following Ministère de l'Environnement standards, including corrosion control guidance consistent with Health Canada requirements.