Rohnert Park Water Hardness & Quality Report (2026)
Water Hardness
7.2 grains per gallon
Source
mixed
pH Level
7.8
neutral = 7.0
Lead
0.006 mg/L
✓ Below action level
TDS
334.2 mg/L
Est. Daily Cost
$0.33
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 Rohnert Park, your appliances are currently losing 16% efficiency due to mineral buildup.
| Appliance | In Rohnert Park | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 5.5 yrs | 8.5 yrs | -35% |
| Washing Machine | 9 yrs | 12 yrs | -25% |
| Water Heater | 10.7 yrs | 15 yrs | -29% |
Regional Water Comparison
How Rohnert Park compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Rohnert Park, California | 123.5 mg/L | 5.6 ppt | 🟠 Hard | mixed |
| Santa Rosa, California | 95.5 mg/L | 4.8 ppt | 🟡 Moderately Hard | mixed |
| Petaluma, California | 48.5 mg/L | 3.4 ppt | 🟢 Soft | mixed |
| Agua Caliente, California | 29 mg/L | 2.9 ppt | 🟢 Soft | mixed |
| Windsor, California | 174 mg/L | 7.1 ppt | 🟠 Hard | mixed |
National Benchmark
How Rohnert Park compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Rohnert Park | 123.5 mg/L | 🟠 Moderate |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Rohnert Park's Water Unique?
Local geology and source profile
Rohnert Park, California, in Sonoma County — the wine country city built as a master-planned community in the 1950s–1960s (developed by Paul Golis as one of California's first fully planned cities), home of Sonoma State University (SSU), a major Sonoma County residential and commercial community in the Santa Rosa–Petaluma corridor, and a diverse Sonoma County community in the heart of California wine country adjacent to the Sonoma–Napa border — draws its municipal water supply from the Russian River (SCWA) and the Cotati–Rohnert Park Valley Basin via the City of Rohnert Park Water Division. Water hardness in Rohnert Park measures 123.5 mg/L — classified as moderately hard.
Rohnert Park's moderate hardness reflects the Sonoma County wine country valley aquifer characteristics. The Sonoma County Water Agency Russian River supply (the Russian River in Sonoma County — draining Mendocino County volcanic terrain and the Sonoma Coast Range — relatively calcareous-poor coastal terrain). The Cotati–Rohnert Park Valley alluvial aquifer draws from the Santa Rosa Plain — Quaternary alluvial fan and valley fill with Pliocene Petaluma Formation calcareous marine basin sediment (moderately calcareous coastal basin formation). The blended Russian River and valley aquifer supply produces the moderate 123.5 mg/L at Rohnert Park.
At 123.5 mg/L, Rohnert Park residents encounter moderate scale accumulation. Monthly cleaning with citric acid solution is recommended for faucet aerators and showerheads. City of Rohnert Park Water Division consistently delivers water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.
Geology & Source: Mixed supply from the Russian River (Sonoma County Water Agency — SCWA) and groundwater (Cotati–Rohnert Park Valley aquifer) via the Rohnert Park Water Division — the Sonoma County central Sonoma Valley corridor (Quaternary volcanic–alluvial Sonoma Valley terrain; Pliocene Petaluma Formation calcareous basin sediment); moderately hard supply at 123.5 mg/L in Sonoma County.