Reston Water Hardness & Quality Report (2026)
Water Hardness
6.9 grains per gallon
Source
reservoir
pH Level
7.7
neutral = 7.0
Lead
0.004 mg/L
✓ Below action level
TDS
224.8 mg/L
Est. Daily Cost
$0.32
energy & soap waste
Source: USGS Water Quality Portal · Updated 2026
0–60
mg/L
Soft
61–120
mg/L
Moderately Hard
121–180
mg/L
Hard
180+
mg/L
Very Hard
Appliance Damage Report
In Reston, your appliances are currently losing 16% efficiency due to mineral buildup.
| Appliance | In Reston | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 5.7 yrs | 8.5 yrs | -33% |
| Washing Machine | 9.2 yrs | 12 yrs | -23% |
| Water Heater | 10.9 yrs | 15 yrs | -27% |
Regional Water Comparison
How Reston compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Reston, Virginia | 118.5 mg/L | 6 ppt | 🟡 Moderately Hard | reservoir |
| Herndon, Virginia | 134 mg/L | 6.9 ppt | 🟠 Hard | reservoir |
| Great Falls, Virginia | 169 mg/L | 8.8 ppt | 🟠 Hard | reservoir |
| Wolf Trap, Virginia | 114.5 mg/L | 5.8 ppt | 🟡 Moderately Hard | reservoir |
| Oak Hill, Virginia | 114.5 mg/L | 5.8 ppt | 🟡 Moderately Hard | reservoir |
National Benchmark
How Reston compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Reston | 118.5 mg/L | 🟡 Low |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Reston's Water Unique?
Local geology and source profile
Reston, Virginia, in Fairfax County — one of the United States' first planned communities (founded 1964 by Robert E. Simon, whose initials gave it the name RES-ton), a major Northern Virginia tech hub, and the future home of the Amazon HQ2 North complex — draws its municipal water supply from the Potomac River via Fairfax Water (Fairfax County Water Authority), treating Potomac River water at the Corbalis and Griffith Water Treatment Plants for Reston and the outer Fairfax County area. Water hardness in Reston measures 118.5 mg/L — classified as moderately hard.
Reston's moderate hardness reflects the Fairfax Water Potomac supply distribution to the outer Fairfax County tech corridor. The Potomac River at the Fairfax Water intakes carries moderate calcareous content from the Shenandoah Valley calcareous carbonates (the Great Valley's Ordovician Edinburg Formation limestone, Silurian Tonoloway Limestone, and Devonian Helderberg Limestone sequence — the dominant calcareous formations of the Shenandoah Valley carbonate belt). Fairfax Water's Corbalis and Griffith plants treat Potomac water effectively, and the Reston distribution — as a planned community with newer underground utilities from the 1960s onward — maintains the treated supply at the moderate 118.5 mg/L.
At 118.5 mg/L, Reston residents encounter moderate scale accumulation. Faucet aerators and showerheads develop deposits after several months — monthly cleaning with citric acid solution is practical maintenance. Fairfax Water consistently delivers water meeting all Virginia DEQ and EPA Safe Drinking Water Act requirements.
Geology & Source: River supply from the Potomac River via the Fairfax Water (Fairfax County Water Authority) Corbalis and Griffith Water Treatment Plants — the outer Fairfax County Reston–Herndon distribution zone; moderately hard supply at 118.5 mg/L in Fairfax County — reflecting the Potomac River supply distribution to the outer Fairfax County tech corridor.