Frederick Water Hardness & Quality Report (2026)

Frederick, Maryland, the Frederick County seat in the Maryland Piedmont and Blue Ridge transition — a historic Maryland city at the crossroads of the National Road and key Civil War campaigns (Antietam, Monocacy) — draws its municipal water supply from the Monocacy River via the City of Frederick Department of Public Works Water Division, treating Monocacy River water at the Frederick Water Treatment Plant. The Monocacy River at Frederick drains the Maryland Great Valley and Frederick Valley. Water hardness in Frederick measures 109 mg/L — classified as moderately hard.

Frederick's moderately soft supply reflects the Monocacy River watershed's Blue Ridge–Great Valley geology. The Monocacy River above Frederick drains: the Maryland Blue Ridge (Proterozoic Catoctin Formation metabasalt and Weverton Quartzite — calcium-poor volcanic and siliceous terrain); the Maryland Great Valley (the Hagerstown Valley — Cambrian Conococheague Limestone and Elbrook Dolomite are major calcareous formations, but the Frederick Valley Triassic–Jurassic redbeds are siliceous); and the Frederick Triassic Basin (Triassic New Oxford Formation — arkosic red sandstone, minor calcareous cement). The Catoctin metabasalt and Triassic arkose terrain contribute little calcium, while only the eastern Great Valley carbonates contribute moderate dissolved calcium — producing a moderately soft 109 mg/L supply.

At 109 mg/L, Frederick residents encounter moderate scale accumulation. Faucet aerators and showerheads develop deposits after several months — monthly cleaning with citric acid solution is practical maintenance. City of Frederick Department of Public Works consistently delivers water meeting all Maryland MDE and EPA Safe Drinking Water Act requirements.