McLean Water Hardness & Quality Report (2026)

McLean, Virginia, in Fairfax County — one of the most affluent communities in the United States (home to CIA headquarters at Langley, numerous US intelligence community offices, and among the highest concentrations of federal agency personnel and government contractors in the country), a premier Northern Virginia community with a significant foreign diplomat and international community — draws its municipal water supply from the Potomac River via Fairfax Water (Fairfax County Water Authority). Water hardness in McLean measures 173 mg/L — classified as hard.

McLean's hard supply — notably harder than the WSSC Potomac zones (Montgomery County 95 mg/L) — reflects the Fairfax Water distribution characteristics in the north Fairfax County McLean zone. The Fairfax Water treats Potomac River supply at its James J. Corbalis Jr. Water Treatment Plant and distributes through north Fairfax County. The McLean distribution zone includes some of the older Fairfax County infrastructure from the 1950s–1970s McLean suburban buildout era (McLean developed as a Washington elite suburb in this period). These older north Fairfax mains accumulate more mineral content than the newer Fairfax County outer suburban zones, producing the hard 173 mg/L at McLean.

At 173 mg/L, McLean residents face regular hard water challenges. Scale deposits form on faucet aerators, showerheads, and appliances within weeks — monthly descaling with citric acid solution is standard maintenance. Fairfax Water consistently delivers water meeting all Virginia DEQ and EPA Safe Drinking Water Act requirements.