Laval Water Hardness & Quality Report (2026)

Laval's drinking water is managed by Ville de Laval, drawing from the Rivière des Prairies (which separates Laval Island from Montréal) and supplementary intake from the St. Lawrence River. Water is treated at two facilities — the Pont Viau and Sainte-Rose water treatment plants — using coagulation, sedimentation, filtration, ozonation, and chloramination, in full compliance with the Guidelines for Canadian Drinking Water Quality (GCDWQ). Hardness measures 118 mg/L (6.9 gpg) — moderately hard by Health Canada classification.

Laval occupies an island in the St. Lawrence Lowlands, a region underlain by Ordovician limestone, dolostone, and shale formations that dissolved over millennia by river and groundwater action. The Rivière des Prairies drains through this carbonate-rich sedimentary basin, picking up dissolved calcium and magnesium as it flows. Laval's supply is chemically similar to Montréal's — both cities draw from the same regional limestone geology — with hardness in the moderate range typical of the greater Montréal watershed.

At 118 mg/L, Laval residents notice moderate limescale accumulation in kettles, on tap aerators, and inside hot water tanks. Kettle descaling with white vinegar or citric acid every six to eight weeks maintains performance. Limescale deposits on hot water tank elements should be inspected annually; periodic tank flushing extends lifespan. For households with new high-efficiency appliances, a scale inhibitor on the main cold water line is a cost-effective preventive measure.