Walnut Creek Water Hardness & Quality Report (2026)
Water Hardness
8.6 grains per gallon
Source
mixed
pH Level
8
neutral = 7.0
Lead
0.007 mg/L
✓ Below action level
TDS
422.7 mg/L
Est. Daily Cost
$0.39
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 Walnut Creek, your appliances are currently losing 20% efficiency due to mineral buildup.
| Appliance | In Walnut Creek | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 4.7 yrs | 8.5 yrs | -45% |
| Washing Machine | 8.2 yrs | 12 yrs | -32% |
| Water Heater | 9.7 yrs | 15 yrs | -35% |
Regional Water Comparison
How Walnut Creek compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Walnut Creek, California | 147 mg/L | 6.3 ppt | 🟠 Hard | mixed |
| Pleasant Hill, California | 144 mg/L | 6.2 ppt | 🟠 Hard | mixed |
| Lafayette, California | 53 mg/L | 3.6 ppt | 🟢 Soft | mixed |
| Alamo, California | 43.5 mg/L | 3.3 ppt | 🟢 Soft | mixed |
| Concord, California | 97 mg/L | 4.8 ppt | 🟡 Moderately Hard | mixed |
National Benchmark
How Walnut Creek compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Walnut Creek | 147 mg/L | 🟠 Moderate |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Walnut Creek's Water Unique?
Local geology and source profile
Walnut Creek, California, in central Contra Costa County at the base of Mount Diablo — a major East Bay suburban center and the hub of the Diablo Valley — draws its municipal water supply from the East Bay Municipal Utility District (EBMUD) Mokelumne River aqueduct (very soft Sierra Nevada source) supplemented by local Walnut Creek groundwater basin wells via EBMUD or the City of Walnut Creek Water Division in a service arrangement with EBMUD. Water hardness in Walnut Creek measures 147 mg/L — classified as moderately hard, substantially harder than EBMUD-only central East Bay cities (Oakland: ~45 mg/L).
Walnut Creek's moderately hard supply — far above EBMUD's soft Mokelumne source — reflects significant local groundwater contribution from the Mount Diablo area. The Walnut Creek Valley is flanked by Mount Diablo (formed of thrust-faulted Franciscan Complex — blueschist, greenschist, serpentinite, chert; Great Valley Sequence calcareous turbidite sandstone and shale; and the Mount Diablo Sandstone). Groundwater in the Walnut Creek alluvial basin acquires dissolved calcium from the calcareous Great Valley Sequence turbidites and serpentinite (calcium-magnesium silicate) that form the Diablo Range foothills. The local Diablo Range groundwater blend raises the finished supply well above the soft EBMUD Mokelumne baseline.
At 147 mg/L, Walnut Creek residents encounter moderate scale accumulation. Faucet aerators and showerheads develop deposits after several months — monthly cleaning with citric acid solution is practical maintenance. EBMUD consistently delivers water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.
Geology & Source: Mixed supply from East Bay Municipal Utility District (EBMUD) Mokelumne River aqueduct and local Walnut Creek Basin groundwater via the City of Walnut Creek Water Division (or EBMUD direct service) — the Sierra Nevada Mokelumne watershed granodiorite and the Diablo Range Mount Diablo Sandstone–Franciscan Complex alluvial fan; moderately hard supply at 147 mg/L in Contra Costa County.