Foster City Water Hardness & Quality Report (2026)
Water Hardness
8.4 grains per gallon
Source
mixed
pH Level
8
neutral = 7.0
Lead
0.007 mg/L
✓ Below action level
TDS
406.9 mg/L
Est. Daily Cost
$0.38
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 Foster City, your appliances are currently losing 19% efficiency due to mineral buildup.
| Appliance | In Foster City | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 4.9 yrs | 8.5 yrs | -42% |
| Washing Machine | 8.3 yrs | 12 yrs | -31% |
| Water Heater | 9.9 yrs | 15 yrs | -34% |
Regional Water Comparison
How Foster City compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Foster City, California | 143 mg/L | 6.2 ppt | 🟠 Hard | mixed |
| Belmont, California | 176 mg/L | 7.1 ppt | 🟠 Hard | mixed |
| San Carlos, California | 163 mg/L | 6.8 ppt | 🟠 Hard | mixed |
| San Mateo, California | 40.5 mg/L | 3.2 ppt | 🟢 Soft | mixed |
| Redwood City, California | 178 mg/L | 7.2 ppt | 🟠 Hard | mixed |
National Benchmark
How Foster City compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Foster City | 143 mg/L | 🟠 Moderate |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Foster City's Water Unique?
Local geology and source profile
Foster City, California, in San Mateo County — a major San Mateo County planned bayfront community (Foster City is a planned community built on a former marsh and bay mudflat on the San Francisco Bay shore — literally built on artificial fill beginning in 1960, one of the most completely planned new cities built in California during the postwar era, named for developer T. Jack Foster), home of a significant technology office presence (Foster City's business parks house major technology companies — the Gilead Sciences headquarters and numerous biotech firms are located in Foster City), a diverse San Mateo County community with a significant Chinese-American, Indian-American, and South Asian-American technology professional population, and a San Francisco Bay lagoon community with an extensive system of waterways — draws its municipal water supply via the Estero Municipal Improvement District (EMID). Water hardness in Foster City measures 143 mg/L — classified as moderately hard.
Foster City's moderate hardness reflects the Peninsula supply blend characteristics. The EMID purchases from the San Francisco Public Utilities Commission (SFPUC) Hetch Hetchy system and blends with local San Mateo County reservoir water. The SFPUC Hetch Hetchy supply (Sierra Nevada calcareous-poor granite, normally very soft) blends with calcareous-moderate local Peninsula reservoir supply, producing the moderate 143 mg/L after treatment.
At 143 mg/L, Foster City residents encounter moderate scale accumulation. Monthly cleaning with citric acid solution is recommended. EMID consistently delivers water meeting all California DDW and EPA Safe Drinking Water Act requirements.
Geology & Source: Mixed supply from the Hetch Hetchy (Sierra Nevada) and San Francisco Peninsula reservoir blend via the Estero Municipal Improvement District (EMID) — the San Mateo County central San Francisco Bay Peninsula (Sierra Nevada calcareous-poor granite and Santa Cruz Mountains calcareous-poor Franciscan Assemblage — the San Mateo County Peninsula mixed supply; EMID blend with treatment); moderately hard supply at 143 mg/L in San Mateo County.