Tamalpais-Homestead Valley Water Hardness & Quality Report (2026)
Water Hardness
10.2 grains per gallon
Source
mixed
pH Level
8.2
neutral = 7.0
Lead
0.008 mg/L
✓ Below action level
TDS
537.2 mg/L
Est. Daily Cost
$0.47
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 Tamalpais-Homestead Valley, your appliances are currently losing 23% efficiency due to mineral buildup.
| Appliance | In Tamalpais-Homestead Valley | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 3.8 yrs | 8.5 yrs | -55% |
| Washing Machine | 7.1 yrs | 12 yrs | -41% |
| Water Heater | 8.6 yrs | 15 yrs | -43% |
Regional Water Comparison
How Tamalpais-Homestead Valley compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Tamalpais-Homestead Valley, California | 174.5 mg/L | 7.1 ppt | 🟠 Hard | mixed |
| Mill Valley, California | 126 mg/L | 5.7 ppt | 🟠 Hard | mixed |
| Larkspur, California | 109 mg/L | 5.2 ppt | 🟡 Moderately Hard | mixed |
| San Rafael, California | 49.5 mg/L | 3.5 ppt | 🟢 Soft | mixed |
| San Anselmo, California | 153.5 mg/L | 6.5 ppt | 🟠 Hard | mixed |
National Benchmark
How Tamalpais-Homestead Valley compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Tamalpais-Homestead Valley | 174.5 mg/L | 🟠 Moderate |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Tamalpais-Homestead Valley's Water Unique?
Local geology and source profile
Tamalpais-Homestead Valley, California, in Marin County — a Marin County unincorporated community on the southeast slope of Mount Tamalpais adjacent to Mill Valley and Corte Madera — receives its water from the Marin Municipal Water District, drawing from the Lagunitas Creek watershed and imported State Water Project supply through the north California distribution.
The hard 174.5 mg/L hardness and TDS of 537.2 mg/L reflect the Marin County supply's hard blended character — the Franciscan Marin Formation provides insoluble dilution from its metamorphic rocks, but the imported State Water Project supply blended with the Lagunitas Creek watershed concentrates dissolved minerals from the Delta agricultural corridor; Marin County's higher TDS relative to hardness reflects the imported water's evaporite mineral load (compare Mill Valley CA: 170/527 in Marin County comparable; Corte Madera CA: 178/547 in Marin County comparable; Tamalpais-Homestead Valley consistent hard from the same Marin County Lagunitas Creek Franciscan insoluble supply). The Marin watershed — Franciscan Marin Formation (insoluble — primary dilutant), Cretaceous Knoxville Formation (slightly calcareous — primary hardness contributor), and Quaternary Lagunitas Creek alluvium and imported State Water Project supply (calcareous — TDS contributor).
At 174.5 mg/L with TDS 537, Tamalpais-Homestead Valley's water is hard — scale builds in appliances. Quarterly descaling is appropriate. The PFAS level of 7.1 ppt warrants a certified drinking water filter. Review Marin Municipal Water District's annual water quality report.
Geology & Source: Tamalpais-Homestead Valley in Marin County draws from the Marin Municipal Water on the Lagunitas Creek watershed (Marin County, north California) — the Marin watershed draws from Franciscan Marin Formation (insoluble) and Cretaceous Knoxville Formation (slightly calcareous) — California Marin County Lagunitas Creek Franciscan insoluble supply produces hard water at 174.5 mg/L with TDS 537.2 mg/L.