Châteauguay Water Hardness & Quality Report (2026)

Châteauguay's drinking water is managed by Ville de Châteauguay, a major south shore suburb of Montréal, drawing from the Rivière Châteauguay via the Châteauguay Water Treatment Plant on the riverbank. Water undergoes coagulation, sedimentation, filtration, UV disinfection, and chloramination, meeting all Guidelines for Canadian Drinking Water Quality (GCDWQ) requirements. Hardness measures 113 mg/L (6.6 gpg) — classified as moderately hard by Health Canada, reflecting the Rivière Châteauguay's moderately mineralised chemistry from its cross-border Appalachian-Lowlands watershed.

The Rivière Châteauguay originates in Lake Châteauguay in northern New York State (Franklin County), draining through the Adirondack foothills and Trenton Group limestone outcrops of the St. Lawrence Lowlands before flowing northward through the Montérégie to its confluence with the St. Lawrence south of Montréal. As the river crosses the Lowlands carbonate plain — underlain by the Ordovician Trenton and Black River limestone and Utica Shale sequence — it picks up moderate dissolved calcium, producing the 113 mg/L recorded at Châteauguay's tap.

At 113 mg/L, Châteauguay residents experience moderate scale deposits in kettles and on tap aerators — descaling every six to eight weeks is adequate. Hot water tanks operate reliably at this hardness. Ville de Châteauguay publishes annual water quality reports following Ministère de l'Environnement standards, and residents in older pre-1970 housing stock along the river corridor are encouraged to follow Health Canada lead precautionary guidance and enquire about lead service line status.