Wilmington Water Hardness & Quality Report (2026)

Wilmington, North Carolina, the largest port city in North Carolina, draws its municipal water supply from the Cape Fear River via the City of Wilmington Public Utilities, operating the Sweeney Water Treatment Plant on the Cape Fear River in New Hanover County. The Cape Fear River drains much of the North Carolina Piedmont and Coastal Plain before reaching Wilmington near the Atlantic coast. Water is treated at the Sweeney facility before distribution throughout the greater Wilmington metropolitan area. Water hardness measures 173.5 mg/L — classified as hard, notably higher than typical Piedmont river supplies.

Wilmington's hard supply — somewhat elevated for a Cape Fear River city — reflects the influence of Coastal Plain calcareous formations through which the Cape Fear River flows in its lower course. While the Cape Fear's upper reach drains the North Carolina Piedmont (Carolina Terrane metavolcanics, Precambrian gneiss — inherently soft terrains), the lower Cape Fear crosses the Cretaceous Peedee Formation and Black Creek Formation — calcareous marine chalk and marl deposits of the southeastern Coastal Plain. The river's residence in and interaction with these calcareous Cretaceous formations increases the dissolved calcium load by the time it reaches the Sweeney intake near Wilmington. The Coastal Plain's flat topography also limits dilution by fresh rainfall.

At 173.5 mg/L, Wilmington residents face regular hard water challenges. Scale deposits form on faucet aerators, showerheads, and shower glass within weeks — monthly cleaning with citric acid solution is a standard maintenance routine. Dishwashers produce better glassware results with rinse-aid, and water heaters benefit from annual inspection for element scale accumulation. City of Wilmington Public Utilities consistently delivers water meeting all North Carolina DEQ and EPA Safe Drinking Water Act requirements.