Dover Water Hardness & Quality Report (2026)

Dover, Delaware, the state capital and Kent County seat — Delaware's state capital and second-largest city, home of Dover Air Force Base (the largest air mobility base in the US, including the Air Force Mortuary Affairs Operations — the primary military mortuary for fallen servicemembers), Dover International Speedway (a major NASCAR venue — the 'Monster Mile'), Delaware State University (a historically Black university), and a historically significant colonial city (Dover was one of the first capitals of the American republic — Delaware ratified the Constitution first in December 1787, making Delaware the 'First State') — draws its municipal water supply from the Columbia Aquifer and Piney Point Formation via the City of Dover Water Division. Water hardness in Dover measures 132 mg/L — classified as moderately hard.

Dover's moderate hardness reflects the central Delaware Coastal Plain aquifer's calcareous-moderate geology. The Columbia Aquifer (Quaternary Columbia Group sand and gravel) and Piney Point Formation (Eocene calcareous sandy limestone of the Chesapeake Group) at Dover–Kent County are: moderately calcareous Coastal Plain sands with calcareous shell fragments and calcareous cement zones; more calcareous than the northern Delaware Coastal Plain communities due to the higher carbonate content in the central Delaware Piney Point formation. City of Dover's treatment of the calcareous-moderate Coastal Plain aquifer produces the moderate 132 mg/L.

At 132 mg/L, Dover residents encounter moderate-to-hard scale accumulation. Monthly cleaning with citric acid solution is recommended. City of Dover Water Division consistently delivers water meeting all Delaware DNREC and EPA Safe Drinking Water Act requirements.