Water heater flush in Leesburg.

Leesburg runs its own water plant on the Potomac, and the Town’s 2025 water quality report puts hardness at typically 100 to 150 parts per million, 5.8 to 8.8 grains per gallon, all of it river water that year. That’s moderately hard to hard: enough to leave sediment in a tank every year, and over the 4 grain mark where Navien puts a tankless on a yearly descale. The Town’s own utilities FAQ says that calcium settles out inside the water heater and turns up as white or pale green specks in faucet strainers, and that white chips can also mean a broken dip tube in the tank. It tells Leesburg residents to drain the heater at least once a year, with the power off on an electric one while it drains and refills.

Outside the town limits, the supplier changes. Loudoun Water, for one, lists Lansdowne among the areas it serves, and its water leans on Potomac water treated by Fairfax Water. The flush rule doesn’t change much across that line, but the hardness figure worth going by is the one from whoever sends your bill.

Most of Leesburg’s houses went up after 1980, the median one in 1996, a bit under half single-family and about three in ten townhouses, with the historic downtown a small and much older exception. In the newer neighborhoods the original heaters are at replacement age or past it, and the date on the tank’s label tells us which side of that line yours is on.