San Bruno Water Hardness & Quality Report (2026)
Water Hardness
9.5 grains per gallon
Source
mixed
pH Level
8.1
neutral = 7.0
Lead
0.008 mg/L
✓ Below action level
TDS
484 mg/L
Est. Daily Cost
$0.43
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 San Bruno, your appliances are currently losing 22% efficiency due to mineral buildup.
| Appliance | In San Bruno | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 4.3 yrs | 8.5 yrs | -49% |
| Washing Machine | 7.6 yrs | 12 yrs | -37% |
| Water Heater | 9.1 yrs | 15 yrs | -39% |
Regional Water Comparison
How San Bruno compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ San Bruno, California | 162 mg/L | 6.8 ppt | 🟠 Hard | mixed |
| South San Francisco, California | 52 mg/L | 3.5 ppt | 🟢 Soft | mixed |
| Millbrae, California | 126.5 mg/L | 5.7 ppt | 🟠 Hard | mixed |
| Burlingame, California | 131.5 mg/L | 5.9 ppt | 🟠 Hard | mixed |
| Pacifica, California | 98 mg/L | 4.9 ppt | 🟡 Moderately Hard | mixed |
National Benchmark
How San Bruno compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ San Bruno | 162 mg/L | 🟠 Moderate |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes San Bruno's Water Unique?
Local geology and source profile
San Bruno, California, in San Mateo County on the San Francisco Peninsula — a diverse San Mateo County community, home of YouTube's world headquarters, the San Francisco International Airport southern approach corridor, and a community known for the 2010 San Bruno natural gas pipeline explosion (Pacific Gas and Electric Company pipeline failure that destroyed 38 homes and killed 8 people) — draws its municipal water supply from the SFPUC (Crystal Springs Reservoir and Hetch Hetchy Aqueduct) via the City of San Bruno Water Division. Water hardness in San Bruno measures 162 mg/L — classified as hard.
San Bruno's hard supply — significantly harder than Daly City (39 mg/L) using the same SFPUC source — reflects the San Mateo County Peninsula distribution infrastructure's substantial mineral accumulation. The SFPUC Crystal Springs supply (from Crystal Springs Reservoir — Santa Cruz Mountains Franciscan Complex and Great Valley Group watershed, calcareous-poor) is very soft at source. However, San Bruno's distribution infrastructure includes older San Mateo County water mains from the 1940s–1970s Peninsula suburban buildout era, accumulating substantial mineral content from the soft source supply. The aged San Mateo County mains in the San Bruno zone produce the hard 162 mg/L.
At 162 mg/L, San Bruno residents face regular hard water challenges. Monthly descaling with citric acid solution is standard maintenance. City of San Bruno Water Division consistently delivers water meeting all California SWRCB and EPA Safe Drinking Water Act requirements.
Geology & Source: Reservoir supply from the SFPUC Hetch Hetchy Aqueduct (Tuolumne River watershed) and Crystal Springs Reservoir via the San Francisco Public Utilities Commission (SFPUC) — the San Mateo County San Bruno–South San Francisco corridor (SFPUC Crystal Springs supply zone — San Mateo County Peninsula watershed + Hetch Hetchy soft supply); hard supply at 162 mg/L — reflecting the San Mateo County distribution infrastructure's significant mineral accumulation.