Saint-Léonard Water Hardness & Quality Report (2026)

Service de l'eau de la Ville de Saint-Léonard, part of Montreal's metropolitan water system, supplies approximately 75,000 residents. The water originates primarily from the St. Lawrence River, treated at the Atwater and Des Baillets facilities serving greater Montreal. This is supplemented by local groundwater wells drawn from the Chateauguay area. The St. Lawrence River watershed is the main source, with its waters flowing through southern Quebec's mixed forest and agricultural lowlands before reaching the intake.

Key rock formations in the St. Lawrence Lowlands include Paleozoic limestones and dolomites from the Ordovician period, notably the Beekmantown Group. These formations create karst aquifers where water easily dissolves minerals. Local groundwater also taps into fractured bedrock aquifers, with glacial deposits influencing the water. This prolonged contact with carbonate-rich strata results in moderately mineralized water, characterized by notable dissolved solids from natural leaching.

This moderately hard water can lead to scale buildup in pipes and appliances like water heaters and dishwashers, potentially reducing their efficiency over time and leaving spots on glassware. You might also notice laundry feeling stiffer and less effective soap lathering, requiring more detergent. Homeowners experiencing these effects might consider a water softener to extend equipment life and improve cleaning. Annual descaling of appliances and hot water tanks is also advised to manage mineral buildup. Montreal's system complies with Health Canada lead guidelines, with median levels around 1-5 µg/L. Treatment processes include coagulation, filtration, chlorination, and ammonia addition for disinfection.