Mercier–Hochelaga-Maisonneuve Water Hardness & Quality Report (2026)

Service de l'eau de la Ville de Montréal provides drinking water to Mercier–Hochelaga-Maisonneuve, a borough in eastern Montreal, Quebec, Canada. The water supply originates from the Des Prairies River, which feeds the Atwater and Charles-J.-Des Baillets treatment plants, and the St. Lawrence River, supplying the Mazière plant. These facilities collectively serve over 1.1 million residents across the island of Montreal and nearby areas. After intake, the raw water undergoes a multi-stage treatment process including screening, ozonation, coagulation, flocculation, sedimentation, dual-media filtration, and finally, chloramination.

The geological landscape of the St. Lawrence River watershed is shaped by its history. Underlying the region are Paleozoic sedimentary formations, specifically Ordovician limestones and dolomites found within the Champlain Sea basin. These bedrock types are rich in minerals like calcium and magnesium. As water flows through these formations, these minerals naturally leach into the surface water, giving the supply its characteristic moderately mineralized profile. This natural buffering from dissolved bicarbonates contributes to the water's overall character.

This moderately hard water can lead to visible limescale buildup on fixtures like faucets and showerheads, as well as inside appliances such as kettles. Over time, this scale can reduce the efficiency of water heaters and dishwashers by as much as 20-30%. You might also notice that laundry feels stiffer, and soaps don't lather as effectively, potentially leaving soap scum behind. Appliances like coffee makers and washing machines are particularly susceptible. While regular descaling with vinegar can help manage buildup, installing a water softener is often recommended for households experiencing dry skin or persistent scale issues. This can help extend the lifespan of your appliances and improve cleaning performance.