Newmarket Water Hardness & Quality Report (2026)

Newmarket's drinking water is managed by York Region, primarily drawing from Lake Ontario via the region's south-to-north transmission system, with a significant proportion of groundwater from the Oak Ridges Moraine aquifer system and underlying Silurian and Ordovician carbonate bedrock wells. Treatment includes coagulation, sedimentation, softening, filtration, UV disinfection, and chloramination, fully meeting the Guidelines for Canadian Drinking Water Quality (GCDWQ). Hardness in Newmarket is 208 mg/L (12.1 gpg) — classified as very hard by Health Canada, elevated well above Lake Ontario's baseline due to the deep carbonate groundwater blending in this northern York Region community.

Newmarket sits at the northern end of York Region, on the southern edge of the Lake Simcoe watershed. The Oak Ridges Moraine — a thick glacial deposit of sand and gravel overlying Silurian and Ordovician limestone bedrock — lies immediately south of Newmarket. Groundwater wells tapping these carbonate formations yield very hard water rich in dissolved calcium and magnesium. As this hard groundwater is blended with Lake Ontario transmission supply in the Newmarket distribution zone, the combined hardness rises well above the southern York Region baseline.

At 208 mg/L, Newmarket residents experience persistent scale build-up on kettle elements, showerheads, and inside hot water tanks — monthly descaling is standard practice. Hot water tank elements accumulate scale quickly; York Region and the City recommend annual inspection and tank flushing to maintain efficiency. A whole-home water softener is a practical and common investment in Newmarket — the combination of hard Lake Ontario supply and even harder local aquifer blending makes Newmarket one of the York Region communities with the most challenging household water quality.