Rockville Water Hardness & Quality Report (2026)
Water Hardness
9.9 grains per gallon
Source
reservoir
pH Level
8.1
neutral = 7.0
Lead
0.007 mg/L
✓ Below action level
TDS
406.2 mg/L
Est. Daily Cost
$0.45
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 Rockville, your appliances are currently losing 23% efficiency due to mineral buildup.
| Appliance | In Rockville | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 4 yrs | 8.5 yrs | -53% |
| Washing Machine | 7.3 yrs | 12 yrs | -39% |
| Water Heater | 8.8 yrs | 15 yrs | -41% |
Regional Water Comparison
How Rockville compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Rockville, Maryland | 169.5 mg/L | 9.3 ppt | 🟠 Hard | reservoir |
| North Bethesda, Maryland | 134 mg/L | 7.2 ppt | 🟠 Hard | reservoir |
| Redland, Maryland | 142 mg/L | 7.7 ppt | 🟠 Hard | reservoir |
| Gaithersburg, Maryland | 121.5 mg/L | 6.5 ppt | 🟠 Hard | reservoir |
| Aspen Hill, Maryland | 95.5 mg/L | 5.1 ppt | 🟡 Moderately Hard | reservoir |
National Benchmark
How Rockville compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Rockville | 169.5 mg/L | 🟠 Moderate |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Rockville's Water Unique?
Local geology and source profile
Rockville, Maryland, the Montgomery County seat — the first town chartered in Maryland (1860), an affluent inner suburb of Washington DC and the hub of the I-270 Technology Corridor — draws its municipal water supply from the Potomac River via the Washington Suburban Sanitary Commission (WSSC Water) Potomac Water Filtration Plant, treating Potomac River water for central and upper Montgomery County including Rockville. Water hardness in Rockville measures 169.5 mg/L — classified as hard.
Rockville's hard supply reflects the Potomac River watershed's calcareous geology and the central Montgomery County distribution characteristics. The Potomac River at the WSSC intake drains the Shenandoah Valley (Cambrian Conococheague Limestone, Ordovician Beekmantown Group dolomite — highly reactive calcareous carbonates) and the Blue Ridge (Catoctin metabasalt — calcium-poor). The calcareous Shenandoah Valley carbonate contribution raises the Potomac River to moderately hard levels at the Great Falls intake. The WSSC distribution network in central Rockville includes infrastructure of varying vintage — the Rockville city and WSSC distribution system serving the dense suburban residential corridors shows moderately elevated hardness consistent with the 169.5 mg/L reading.
At 169.5 mg/L, Rockville residents face regular hard water challenges. Scale deposits form on faucet aerators, showerheads, and appliances within weeks — monthly descaling with citric acid solution is standard maintenance. WSSC Water consistently delivers water meeting all Maryland MDE and EPA Safe Drinking Water Act requirements.
Geology & Source: River supply from the Potomac River via the Washington Suburban Sanitary Commission (WSSC Water) Potomac water filtration plant — the upper Potomac watershed (Blue Ridge Catoctin metabasalt, Shenandoah Valley Cambrian–Ordovician carbonates) distribution to central Montgomery County; hard supply at 169.5 mg/L in Montgomery County.