Alum Rock Water Hardness & Quality Report (2026)
Water Hardness
5.4 grains per gallon
Source
mixed
pH Level
7.6
neutral = 7.0
Lead
0.004 mg/L
✓ Below action level
TDS
230.5 mg/L
Est. Daily Cost
$0.25
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 Alum Rock, your appliances are currently losing 12% efficiency due to mineral buildup.
| Appliance | In Alum Rock | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 6.5 yrs | 8.5 yrs | -24% |
| Washing Machine | 10.2 yrs | 12 yrs | -15% |
| Water Heater | 11.9 yrs | 15 yrs | -21% |
Regional Water Comparison
How Alum Rock compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Alum Rock, California | 93 mg/L | 4.7 ppt | 🟡 Moderately Hard | mixed |
| San Jose, California | 189.5 mg/L | 7.5 ppt | 🔴 Very Hard | mixed |
| Milpitas, California | 140 mg/L | 6.1 ppt | 🟠 Hard | mixed |
| Santa Clara, California | 79 mg/L | 4.3 ppt | 🟡 Moderately Hard | mixed |
| Campbell, California | 80.5 mg/L | 4.3 ppt | 🟡 Moderately Hard | mixed |
National Benchmark
How Alum Rock compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Alum Rock | 93 mg/L | 🟡 Low |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Alum Rock's Water Unique?
Local geology and source profile
Alum Rock, California, in Santa Clara County — an unincorporated Santa Clara County community adjacent to East San Jose and Evergreen in the east San Jose foothills — receives its water from San Jose Water, drawing from the Hetch Hetchy Aqueduct (Sierra Nevada via SFPUC) and local Santa Clara Valley groundwater wells (Santa Clara Valley Water District imports) through the east San Jose distribution system.
The moderately soft 93 mg/L hardness and TDS of 230.5 mg/L (elevated TDS relative to hardness) reflect the east San Jose mixed supply — blending soft Hetch Hetchy Sierra Nevada water (insoluble Cretaceous granodiorite) with moderately calcareous local Santa Clara Valley alluvial groundwater (developed in calcareous alluvial sediments derived from the Diablo Range calcareous formations). The blended supply produces the east San Jose moderately soft character.
At 93 mg/L, Alum Rock's water is moderately soft — light scale forms slowly in appliances, dishwashers remain efficient, and bathroom fixtures need occasional cleaning. Semi-annual descaling is appropriate. The PFAS level of 4.7 ppt warrants a certified drinking water filter — the Santa Clara County east San Jose industrial corridor and the South Bay PFAS background from Moffett Federal Airfield (Mountain View — AFFF, a significant PFAS source for the Santa Clara Valley aquifer) contribute to Alum Rock's readings.
Geology & Source: Alum Rock in Santa Clara County draws from San Jose Water on the Hetch Hetchy Aqueduct and local wells (Santa Clara County, central California) — the Hetch Hetchy delivers Sierra Nevada snowmelt (Cretaceous El Capitan Granodiorite — insoluble) blended with local Santa Clara Valley alluvial groundwater — California Santa Clara County Hetch Hetchy-local aquifer supply produces moderately soft water at 93 mg/L with TDS 230.5 mg/L.