Ahuntsic-Cartierville Water Hardness & Quality Report (2026)

The drinking water for Ahuntsic-Cartierville, a borough of Montreal, Quebec, Canada, is provided by the City of Montreal's Service de l'eau. The supply is drawn from the St. Lawrence River at two primary intake points: the Atwater treatment plant serving the western part of the island including Ahuntsic-Cartierville, and the Charles-J.-Des Baillets plant for eastern sectors. Raw water is abstracted from the river, which serves as the sole source for the island's 1.8 million residents across Montreal's network. No groundwater or reservoirs are used. The St. Lawrence River watershed encompasses over 1 million square kilometers, draining the Great Lakes basin and Appalachian highlands into the Atlantic.

Underlying geology features Ordovician limestone and dolostone formations in the lowlands, with upstream contributions from Precambrian Shield granites and metamorphic rocks. Glacial scouring during the Pleistocene exposed carbonate bedrock, allowing natural dissolution of minerals into the river flow. This sedimentary geology results in a moderately mineralised supply prone to elevated calcium and magnesium content.

Moderately hard water leads to noticeable limescale buildup on faucets, showerheads, and inside pipes over time, reducing water flow and efficiency. Appliances like dishwashers, washing machines, and water heaters are most affected, with shortened lifespan and higher energy costs due to mineral deposits insulating heating elements. Maintenance tips include regular vinegar descaling of fixtures, installing mesh screens on aerators, and flushing water heaters annually. A water softener is recommended for households experiencing dry skin, soap scum, or appliance issues to extend equipment life and improve cleaning performance. Montreal's treated water typically has a pH of 7.5–8.5 for corrosion control. The utility complies with Health Canada's guidelines for lead and copper through orthophosphate dosing and pipe replacement programs, with lead levels well below 0.010 mg/L action levels in recent monitoring. No notable PFAS exceedances reported; trace organics are managed via advanced filtration. Treatment at plants involves screening, ozonation, dual-media filtration, UV disinfection, and chloramination. Annual quality reports confirm consistent compliance across 200+ parameters, with primary concerns limited to occasional taste/odor from algae.