Arlington Water Hardness & Quality Report (2026)

Arlington County, Virginia is served by the Washington Aqueduct, a division of the Baltimore District, U.S. Army Corps of Engineers. The utility draws its primary water supply from the Potomac River and treats it at the Dalecarlia Water Treatment Plant in Washington, D.C., using coagulation, sedimentation, filtration, and disinfection. Treated water is conveyed via pipeline to Arlington County, serving approximately 215,000 residents. The utility operates under federal oversight and publishes regular water quality reports.

The Potomac River watershed drains the Piedmont and Blue Ridge regions of Virginia, Maryland, and West Virginia, flowing through areas underlain by Paleozoic sedimentary rocks including limestone and dolomite formations. These carbonate-rich bedrock units contribute dissolved minerals to the river, resulting in a moderately mineralised water supply. The prevalence of limestone and dolomite in the Potomac basin's subsurface naturally produces moderate hardness characteristics through carbonate dissolution as water moves through the watershed.

At moderate hardness levels, Arlington residents may experience scale buildup in water heaters, kettles, and appliances over time. Soap and detergent efficiency is somewhat reduced, and mineral deposits can accumulate on fixtures and in pipes. Most households do not require a water softener, though some residents choose point-of-use or whole-house treatment for aesthetic reasons or to extend appliance lifespan. Regular descaling of water heaters and periodic cleaning of aerators help manage mineral accumulation. The Dalecarlia treatment plant maintains compliance monitoring for lead and copper under the Lead and Copper Rule; the utility has reported disinfection byproducts including bromodichloromethane above EPA health-based guidelines, and residents can obtain detailed annual Consumer Confidence Reports from the utility.