Nepean Water Hardness & Quality Report (2026)

Nepean (now amalgamated into the City of Ottawa) receives its drinking water through City of Ottawa Water Services, drawing from the Ottawa River via the Lemieux Island and Britannia water treatment plants — the same sources supplying the broader Ottawa area. Treatment includes conventional coagulation, sedimentation, filtration, UV disinfection, and chloramination, fully complying with the Guidelines for Canadian Drinking Water Quality (GCDWQ). Water hardness in the Nepean distribution zone is measured at 123 mg/L (7.2 gpg) — classified as hard by Health Canada, moderately elevated compared to the Ottawa city-wide average of approximately 88 mg/L.

The elevated hardness in the Nepean distribution zone reflects the geological character of western Ottawa, where the distribution network passes through areas with Ordovician limestone and dolostone outcrops and where local groundwater blending from carbonate aquifers can raise measured hardness above the Ottawa River baseline. The Ottawa River drains both the Precambrian Shield to the north and Paleozoic limestone formations to the south — the balance of these two geologically contrasting inflows shapes hardness levels across Ottawa's distribution zones.

At 123 mg/L, Nepean homes experience moderate scale build-up on kettle elements, tap aerators, and showerhead nozzles — descaling every six to eight weeks is advisable. Hot water tanks accumulate scale deposits on heating elements over time, reducing efficiency; Ottawa Water Services recommends periodic inspection and flushing. Ottawa Water Services also provides guidance on lead testing for older Nepean properties built before 1990, in compliance with Health Canada guidelines for drinking water quality.