Petworth Water Hardness & Quality Report (2026)

DC Water (District of Columbia Water and Sewer Authority) provides water service to Petworth and all of Washington, D.C., serving approximately 700,000 residents across the city's 68 square miles. The primary source is the Potomac River, with raw water intake at the Dalecarlia Treatment Plant (northwest D.C., capacity 200 million gallons per day) and the Potomac Treatment Plant (near Great Falls, capacity 300 million gallons per day). These plants treat surface water from the 130-mile Potomac River, which originates in the Potomac Highlands of West Virginia and flows southeast to Chesapeake Bay. No groundwater or reservoirs are used; the supply is purely river-sourced.

The Potomac River watershed spans 14,670 square miles across four states and D.C., encompassing diverse geology from the folded Appalachians to coastal plain sediments. Upper basin rocks include resistant quartzites and shales of the Ordovician Martinsburg Formation, while tributaries like the Shenandoah cut through Paleozoic limestones such as the Devonian Keyser Formation, releasing calcium and magnesium. This karst-influenced terrain and seasonal flow variations result in moderately mineralised water, peaking in warmer months due to lower dilution and higher evaporation.

Moderately hard water in Petworth leads to moderate scale buildup in pipes, water heaters, dishwashers, and washing machines, reducing efficiency and lifespan by 20–30% over time. Soap scum on fixtures, drier skin and hair, and spotted dishes are common. Annual descaling of appliances, vinegar rinses for bathrooms, and low-flow aerators help mitigate issues. A water softener is recommended for households with scaling concerns. DC Water's tap water has a pH of 7.4–8.0; the utility complies with the Lead and Copper Rule, with lead below action levels. No PFAS exceedances reported in recent CCRs; trace levels are treated via granular activated carbon. Treatment includes ozonation, chloramination, and UV disinfection.