Foggy Bottom Water Hardness & Quality Report (2026)

DC Water (District of Columbia Water and Sewer Authority) serves Foggy Bottom and all of Washington, D.C. The utility draws water primarily from the Potomac River via surface water intakes, supplemented by groundwater sources. The main treatment facilities include the Dalecarlia Water Treatment Plant and the McMillan Water Treatment Plant. Foggy Bottom, located in the central part of the District, receives treated water through DC Water's distribution network. The utility publishes an annual Consumer Confidence Report detailing compliance with Safe Drinking Water Act standards, including lead and copper monitoring across the District.

Foggy Bottom's water supply originates in the Potomac River watershed, which drains the Piedmont and Appalachian regions. The underlying geology of Washington, D.C. consists of Piedmont metamorphic rocks to the north and Coastal Plain sediments (Cretaceous and Tertiary age) to the south. These formations, particularly carbonate-rich strata and clay layers, contribute dissolved minerals — primarily calcium and magnesium — to the water supply. The moderately hard character of DC's water reflects the mineral composition of both the Potomac River and local aquifer systems.

At moderately hard levels, Foggy Bottom residents may notice spotting on glassware and dishes, particularly in warmer months when hardness peaks. Soap and detergent efficiency is reduced, and some scaling may occur on faucets and in pipes over time. DC Water reports tap water hardness typically ranges from 70 to 120 mg/L (3 to 9 grains per gallon), classifying the supply as moderately hard. Most residents do not require water softening, though some may choose point-of-use softeners or filters for aesthetic reasons; seasonal hardness variation is notable, with levels increasing in warmer months and decreasing in winter.