Dale City Water Hardness & Quality Report (2026)

Virginia American Water's Prince William District (PWSID 6153625) serves Dale City and surrounding Prince William County — zip codes 20112, 22192, and 22193 — with an average daily supply of 6.5 million gallons. The sole source is the Occoquan Reservoir, a surface impoundment in the northern Virginia Piedmont. Water is treated at a Fairfax Water treatment plant before distribution through the consecutive system to residents across the service area.

The Occoquan Reservoir watershed encompasses the northern Piedmont physiographic province of Virginia, where Precambrian metamorphic bedrock — comprising schist and phyllite — and Paleozoic metasedimentary formations dominate. Weathering of these mineral-rich rocks releases dissolved calcium and magnesium into surface runoff, creating a moderately mineralized supply characteristic of the region. This geology naturally imparts moderate hardness to the reservoir water at levels typical of Virginia Piedmont surface waters.

At the moderately soft classification (74 mg/L), Dale City water causes limited scale buildup on fixtures and appliances over time, with effects less severe than in hard-water areas. Soap and detergent efficiency is slightly reduced, and water heaters may accumulate minor deposits. A water softener may be considered by households concerned with scale on high-use appliances such as dishwashers and washing machines; regular descaling of kettles and showerheads helps maintain efficiency. The treated water maintains a neutral pH of 7.4 and meets all Safe Drinking Water Act standards; lead and copper are not detected at the 90th percentile, fluoride is supplemented to 0.7 mg/L, nitrates range from 0.62–1.30 mg/L (well below the 10 mg/L MCL), and chlorine residual averages 2.5 mg/L in the distribution system.