Cary Water Hardness & Quality Report (2026)

Cary, North Carolina draws its municipal water supply from the Town of Cary Water Resources, sourcing raw surface water from B. Everett Jordan Lake — a US Army Corps of Engineers reservoir on the Haw River in Chatham and Durham Counties — and from Richland Creek via local intake infrastructure in Wake County. Jordan Lake serves as the primary drinking water reservoir for the Research Triangle region, managed jointly by several regional utilities. Raw water is treated at the E.M. Johnson Water Treatment Plant before distribution throughout Cary's large and rapidly growing service area. Water hardness in Cary measures 120.5 mg/L — classified as moderately hard.

Cary's moderate hardness reflects the geology of the upper Cape Fear watershed above Jordan Lake. The Haw River drains the central North Carolina Piedmont — a diverse geological province encompassing the Carolina Slate Belt (ancient Precambrian metavolcanic and metasedimentary rocks), granitic gneiss complexes, and Triassic rift basin sediments (the Deep River Triassic basin's red beds and fluvial sandstone). While the dominant Piedmont crystalline terrain is relatively calcium-poor, the Triassic basin sediments and localised limestone bodies contribute modest dissolved calcium bicarbonate, producing a moderately hard supply in the Jordan Lake watershed.

With hardness at 120.5 mg/L, Cary residents encounter moderate scale accumulation in household use. Faucet aerators and showerheads develop deposits over several months — monthly or bi-monthly cleaning with citric acid or white vinegar is a practical routine. Dishwashers produce cleaner glassware with standard rinse-aid, and water heaters benefit from an annual inspection for element scale. Cary's Water Resources Department consistently delivers high-quality water meeting all North Carolina DEQ and EPA Safe Drinking Water Act requirements, and the town has received regional water quality awards.