Larkspur Water Hardness & Quality Report (2026)
Water Hardness
6.4 grains per gallon
Source
mixed
pH Level
7.7
neutral = 7.0
Lead
0.005 mg/L
✓ Below action level
TDS
283.4 mg/L
Est. Daily Cost
$0.29
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 Larkspur, your appliances are currently losing 15% efficiency due to mineral buildup.
| Appliance | In Larkspur | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 6 yrs | 8.5 yrs | -29% |
| Washing Machine | 9.6 yrs | 12 yrs | -20% |
| Water Heater | 11.2 yrs | 15 yrs | -25% |
Regional Water Comparison
How Larkspur compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Larkspur, California | 109 mg/L | 5.2 ppt | 🟡 Moderately Hard | mixed |
| Mill Valley, California | 126 mg/L | 5.7 ppt | 🟠 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 |
| Novato, California | 110.5 mg/L | 5.3 ppt | 🟡 Moderately Hard | mixed |
National Benchmark
How Larkspur compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Larkspur | 109 mg/L | 🟡 Low |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Larkspur's Water Unique?
Local geology and source profile
Larkspur, California, in Marin County — a Marin County city adjacent to Corte Madera and San Anselmo on the north San Francisco Bay — receives its water from the Marin Municipal Water District, drawing from Bon Tempe Lake or Kent Lake (Marin County) through the north San Francisco Bay distribution.
The moderately hard 109 mg/L hardness and TDS of 283.4 mg/L are slightly harder than expected for the MMWD Franciscan Complex insoluble supply — the Cretaceous Franciscan Complex produces soft to moderate water, and Larkspur's slightly higher hardness may reflect blending with the adjacent state-imported supply or distribution residence time contacts (compare San Anselmo CA: 76/156 in Marin County on the same MMWD supply softer; Larkspur harder end of the MMWD distribution). The Bon Tempe-Kent system at Marin County — Cretaceous Franciscan Complex (insoluble — primary dilutant), Jurassic Coast Range Ophiolite (ultramafic insoluble — secondary dilutant), and Quaternary Marin alluvium (slightly calcareous — primary hardness contributor).
At 109 mg/L with TDS 283, Larkspur's water is moderately hard — scale builds in kettles and appliances over months, dishwashers benefit from rinse aid, and faucet aerators need periodic cleaning. Quarterly descaling is appropriate. The PFAS level of 5.2 ppt warrants a certified drinking water filter — the Marin County north San Francisco Bay urban-industrial corridor contribute to Larkspur's readings.
Geology & Source: Larkspur in Marin County draws from the Marin Municipal Water District on Bon Tempe Lake or Kent Lake (Marin County, north San Francisco Bay, California) — the Bon Tempe-Kent watershed drains Cretaceous Franciscan Complex (insoluble) and Jurassic Coast Range Ophiolite (ultramafic — insoluble) — California Marin County MMWD Franciscan Complex Cretaceous insoluble supply produces moderately hard water at 109 mg/L with TDS 283.4 mg/L.