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

Rivière-des-Prairies–Pointe-aux-Trembles receives its drinking water through Ville de Montréal — Direction de l'eau potable, served from Montréal's integrated municipal network drawing from the St. Lawrence River and Rivière des Prairies via the Atwater, DesBaillets, and Charles-J. Des Baillets water treatment plants. Treatment includes ozonation, biofiltration, UV disinfection, and chloramination, meeting all Guidelines for Canadian Drinking Water Quality (GCDWQ) standards. Hardness in this east-end borough's distribution zone is 70.5 mg/L (4.1 gpg) — classified as moderately hard by Health Canada, consistent with the softened Montréal distribution zones north of the St. Lawrence.

Rivière-des-Prairies–Pointe-aux-Trembles borders the Rivière des Prairies to the north and the St. Lawrence River to the south, sitting at Montréal island's east end. The borough's distribution zone draws a significant share from the Rivière des Prairies intake influenced by Precambrian Shield tributaries from the Laurentian Highlands, which dilute the harder Ordovician limestone-influenced St. Lawrence baseline. The resulting blend produces the 70.5 mg/L softened supply characteristic of Montréal's east-end Rivière-des-Prairies corridor.

At 70.5 mg/L, residents see only light scale deposits in kettles and on tap aerators — occasional descaling two to three times a year is adequate. Hot water tanks operate efficiently at this hardness without scale treatment. As with all Montréal boroughs, Montréal's Direction de l'eau potable advises residents in older housing to follow Health Canada precautionary guidance on lead and to enquire about lead service line replacement, given the prevalence of pre-1970 plumbing in portions of this largely working-class east-end community.