Chantilly Water Hardness & Quality Report (2026)

Chantilly, Virginia is served by Fairfax Water, the primary utility for Fairfax County. The utility operates four water treatment plants: the Frederick P. Griffith Jr. plant treating water from the Occoquan Reservoir, and three Potomac River facilities — the James J. Corbalis Jr., McMillan, and Dalecarlia plants. These facilities feed an interconnected distribution system serving over 2 million people across the region; raw water is drawn from two primary sources, the Potomac River and the Occoquan Reservoir, fed by the Occoquan River.

Chantilly's water supply originates in the Potomac River and Occoquan Reservoir watersheds, which drain the Piedmont and Blue Ridge regions of Northern Virginia. The underlying geology consists primarily of Paleozoic-age carbonate rocks — limestone and dolomite — and siliciclastic formations. As water travels through these mineral-rich formations, it dissolves significant quantities of calcium and magnesium, resulting in a hard water supply. Fairfax Water's supply is classified as hard, typically ranging from 5 to 10 grains per gallon (84–170 mg/L).

At this hardness level, Chantilly residents commonly observe white mineral deposits on dishware, fixtures, and appliances, and experience reduced soap effectiveness. Scale buildup in water heaters and potential plumbing maintenance issues are typical concerns. A water softener is recommended, particularly for households with older appliances or those sensitive to mineral accumulation; commercial descaling products help manage residue on surfaces. Fairfax Water's quality meets or exceeds all federal and state standards; the utility tests for approximately 177 compounds, and the 2025 Annual Water Quality Report is available on the utility's website.