Rivière-des-Prairies–Pointe-aux-Trembles Water Hardness & Quality Report (2026)

The drinking water for Rivière-des-Prairies–Pointe-aux-Trembles, a borough of the City of Montreal, Quebec, Canada, is provided by the Ville de Montréal water utility. Water is sourced from the St. Lawrence River, with intake and treatment handled at major facilities such as the Charles-J.-Des Baillets Water Treatment Plant and the Atwater Treatment Plant. This utility serves the entire Island of Montreal, including this eastern borough, distributing water through extensive municipal networks with regular quality monitoring. The watershed encompasses the vast St. Lawrence River basin, with local inputs from the Rivière des Prairies, channeling waters from the Ottawa River system.

Regional geology is dominated by Paleozoic sedimentary rocks, including Ordovician limestones, dolomites, and shales of the St. Lawrence Platform, overlaying the Precambrian Canadian Shield to the north. These carbonate formations naturally impart minerals to the river water, yielding a moderately mineralized supply typical of lowland river systems in this area. This geology is the primary reason for the water's mineral content, as it lacks reliance on groundwater aquifers for its supply.

Moderately hard water in this range promotes moderate limescale buildup in appliances like kettles, dishwashers, and washing machines, reducing efficiency over time and increasing energy use. Hot water heaters and coffee makers are particularly affected, with visible deposits forming inside pipes and fixtures. Regular descaling with vinegar and using detergent formulated for hard water can help mitigate issues. A water softener is often recommended for households with these concerns to extend appliance life and improve cleaning performance. Montreal's water maintains a pH typically around 7.5–8.5 post-treatment, with multi-barrier processes including screening, ozonation, UV disinfection, and chloramination at plants like Des Baillets. In 2022, exceedances of maximum acceptable lead concentrations occurred in some samples, prompting pipe replacement efforts.