Cupertino Water Hardness & Quality Report (2026)
Water Hardness
3.6 grains per gallon
Source
mixed
pH Level
7.4
neutral = 7.0
Lead
0.003 mg/L
✓ Below action level
TDS
139.7 mg/L
Est. Daily Cost
$0.17
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 Cupertino, your appliances are currently losing 8% efficiency due to mineral buildup.
| Appliance | In Cupertino | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 7.6 yrs | 8.5 yrs | -11% |
| Washing Machine | 11.3 yrs | 12 yrs | -6% |
| Water Heater | 13.1 yrs | 15 yrs | -13% |
Regional Water Comparison
How Cupertino compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Cupertino, California | 62 mg/L | 3.8 ppt | 🟡 Moderately Hard | mixed |
| Sunnyvale, California | 35.5 mg/L | 3 ppt | 🟢 Soft | mixed |
| Saratoga, California | 109 mg/L | 5.2 ppt | 🟡 Moderately Hard | mixed |
| Mountain View, California | 112.5 mg/L | 5.3 ppt | 🟡 Moderately Hard | mixed |
| Santa Clara, California | 79 mg/L | 4.3 ppt | 🟡 Moderately Hard | mixed |
National Benchmark
How Cupertino compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Cupertino | 62 mg/L | 🟡 Low |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
Bring Badger-quality water to your Cupertino home
Shop water softeners on Amazon.com →
What Makes Cupertino's Water Unique?
Local geology and source profile
Cupertino, California, in Santa Clara County in the heart of Silicon Valley — the global headquarters of Apple Inc. and one of the most affluent and technologically significant communities on Earth — draws its municipal water supply from the San Francisco Public Utilities Commission (SFPUC) Hetch Hetchy Regional Water System (Tuolumne River) and local Santa Clara Valley Groundwater Basin via San Jose Water (SJW) or California Water Service, serving the Cupertino area of the south Santa Clara Valley. Water hardness in Cupertino measures 62 mg/L — classified as moderately soft.
Cupertino's moderate softness reflects the south Santa Clara Valley supply blend's favorable Hetch Hetchy fraction. The SFPUC Hetch Hetchy water (Tuolumne River from Hetch Hetchy Reservoir, Yosemite — draining Cretaceous Sierra Nevada Batholith granodiorite — very soft, 25–40 mg/L source) is the dominant supply for much of the SFPUC peninsula and Santa Clara Valley system. The local Santa Clara Valley Groundwater Basin in Cupertino (the Cupertino sub-basin of the Santa Clara Plain Quaternary alluvial fill) contributes moderate calcareous groundwater from the limestone and calcareous serpentinite of the adjacent Diablo Range foothills. The blend with the dominant soft Hetch Hetchy supply produces the moderate 62 mg/L.
With hardness at 62 mg/L, Cupertino residents enjoy moderately soft water. San Jose Water and California Water Service consistently deliver water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.
Geology & Source: Mixed supply from the Hetch Hetchy Regional Water System (SFPUC) Tuolumne River and local Santa Clara Valley groundwater (Santa Clara Basin) via the San Jose Water (SJW) Cupertino area or California Water Service — the south Santa Clara Valley Cupertino distribution; moderately soft supply at 62 mg/L in Santa Clara County.