Water heater flush in Philomont.

A county brochure says about a quarter of Loudoun residents depend on groundwater, mostly in the western and northern parts, and most of them on a private well on their own lot. Philomont sits in the center of the Loudoun Valley, so work out first which kind of house you have. A well has no utility report behind it. The brochure adds that yields vary because the water comes from fractures in bedrock, so the only word on one well’s minerals is its own test.

If your bill comes from Loudoun Water, the hardness answer is a detour. Look for hardness in its 2025 report and it isn’t there; the utility’s own water quality page directs you to Fairfax Water’s Corbalis data instead. We use what you have: your test, or the Corbalis data for a Loudoun Water address. We don’t do well work, so for a well this is advice only: test it, then set the flush by the result.

Tank age is the other half. The median owner home in ZIP 20132, the Purcellville ZIP area Philomont sits in, dates to 2000, about 24 percent of homes there predate 1980, and nearly half went up since 2000. A tank that has gone unflushed in a house that age is likely the second or third one in it. On an electric tank, sediment piles over the lower element; on a propane tank, it sits between the burner and the water.

Early fall is the window. At the Purcellville station the median first fall low of 32F lands on October 25, and the winter ahead brings 4,942 heating degree days. A flush now, with the anode rod and relief valve checked, puts what drains out in front of you before the hard cold and the heavy use arrive.