Great Falls Water Hardness & Quality Report (2026)

Fairfax Water supplies Great Falls, Virginia, and the surrounding Fairfax County area. The utility draws its water from two main sources: the Potomac River and the Occoquan Reservoir, which is fed by the Occoquan River. Fairfax Water operates four water treatment plants to serve its customers. Water from the Occoquan Reservoir is treated at the Frederick P. Griffith Jr. plant, while water from the Potomac River is processed at three other facilities: the James J. Corbalis Jr., McMillan, and Dalecarlia plants. These plants feed into a shared distribution network that provides water to the entire county.

The watershed feeding the Potomac River and Occoquan Reservoir traverses terrain characterized by Precambrian metamorphic rocks, including schist and gneiss, as well as Paleozoic sedimentary formations. This geological makeup is typical for the Northern Virginia piedmont region. As groundwater and stormwater runoff travel through these rock layers, they pick up dissolved minerals, particularly calcium and magnesium. These naturally occurring minerals contribute to the water's moderately hard quality, a common trait in this area.

Homeowners in Great Falls might notice white mineral deposits, commonly known as scale, forming on faucets, showerheads, dishes, and inside appliances like water heaters and dishwashers. You may also find that soaps and detergents don't lather as effectively. While not strictly necessary, installing a water softener can help extend the life of your appliances, boost the cleaning power of soaps, and reduce the buildup of scale. Existing scale deposits can be removed using commercial descaling solutions. Fairfax Water confirms its water quality consistently exceeds federal and state standards, and its source waters and distribution system are free of lead pipe.