Millbrae Water Hardness & Quality Report (2026)
Water Hardness
7.4 grains per gallon
Source
mixed
pH Level
7.9
neutral = 7.0
Lead
0.006 mg/L
✓ Below action level
TDS
345.1 mg/L
Est. Daily Cost
$0.34
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 Millbrae, your appliances are currently losing 17% efficiency due to mineral buildup.
| Appliance | In Millbrae | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 5.4 yrs | 8.5 yrs | -36% |
| Washing Machine | 8.9 yrs | 12 yrs | -26% |
| Water Heater | 10.5 yrs | 15 yrs | -30% |
Regional Water Comparison
How Millbrae compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Millbrae, California | 126.5 mg/L | 5.7 ppt | 🟠 Hard | mixed |
| Burlingame, California | 131.5 mg/L | 5.9 ppt | 🟠 Hard | mixed |
| San Bruno, California | 162 mg/L | 6.8 ppt | 🟠 Hard | mixed |
| South San Francisco, California | 52 mg/L | 3.5 ppt | 🟢 Soft | mixed |
| San Mateo, California | 40.5 mg/L | 3.2 ppt | 🟢 Soft | mixed |
National Benchmark
How Millbrae compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Millbrae | 126.5 mg/L | 🟠 Moderate |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Millbrae's Water Unique?
Local geology and source profile
Millbrae, California, in San Mateo County on the San Francisco Bay Peninsula adjacent to San Francisco International Airport (SFO) — a Caltrain-accessible South Bay community known for its hillside residential neighborhoods and proximity to the airport corridor — receives its municipal water from California Water Service (Cal Water), which draws from the Crystal Springs Reservoir system on the San Mateo watershed and receives supplemental supply from the San Francisco Public Utilities Commission (SFPUC) Hetch Hetchy regional system. Cal Water's Peninsula district blends both local and imported Bay Area supply sources.
The moderately hard 126.5 mg/L hardness and TDS of 345.1 mg/L are higher than the typical SFPUC Hetch Hetchy baseline (~25–50 mg/L), reflecting the Crystal Springs Reservoir component and distribution system mineral additions. The Crystal Springs Reservoir on the San Andreas Fault zone draws from the Santa Cruz Mountains — a landscape of Franciscan Complex (mélange of chert, greenstone, serpentinized peridotite) and overlying Coast Range Eocene and Miocene marine sedimentary rocks. While the Franciscan itself is not carbonate-rich, the coastal marine sedimentary formations contributing to the watershed add moderate mineral content. The Cal Water Peninsula distribution network's interaction with the blended SFPUC-Crystal Springs supply produces the moderately hard finished character at Millbrae.
At 126.5 mg/L, Millbrae's water is moderately hard — manageable for everyday household use. Scale builds in kettles and coffee machines over months, the dishwasher benefits from rinse aid, and bathroom fixtures develop calcium deposits. Quarterly descaling of heating appliances is the standard schedule. The PFAS level of 5.7 ppt warrants a certified drinking water filter — the SFO airport corridor, Cal Water's regional distribution infrastructure serving the Bay Area industrial zone, and the broader Peninsula's tech and industrial campuses contribute to the PFAS background in this San Mateo County service area.
Geology & Source: Millbrae in San Mateo County is served by California Water Service (Cal Water) drawing from the Crystal Springs Reservoir (San Mateo watershed) and SFPUC Hetch Hetchy import — the Crystal Springs watershed drains the Santa Cruz Mountains over Franciscan Complex (chert, greenstone, serpentinite) and Coast Range sedimentary rocks — mixed Bay Area supply produces moderately hard water at 126.5 mg/L with TDS 345 mg/L in this San Francisco Bay Peninsula community.