What San Jose Residents Should Know
San Jose's water supply is uniquely complex, with different neighborhoods receiving water from different sources. Approximately 40% comes from local mountain reservoirs, 40% is imported through the State Water Project and federal Central Valley Project, and 20% comes from valley groundwater. This mix of sources creates varying water quality profiles across the city.
While water quality generally meets federal and state standards across San Jose, several challenges exist. Silicon Valley's industrial history has left a legacy of groundwater contamination in certain areas, with emerging concerns about PFAS ("forever chemicals") detected in some wells. Additionally, neighborhoods with older infrastructure may have lead service lines or lead plumbing components in buildings constructed before 1986.
Recent testing shows generally safe lead levels, but drought conditions have occasionally increased mineral concentrations and contaminant levels in local supplies. The complex water source mix means your particular water quality can vary based on your neighborhood and whether you're primarily receiving groundwater, surface water, or imported water.
Key Contaminants Found
These substances have been detected in San Jose's water supply at levels that may be concerning for some residents.
PFAS ("Forever Chemicals")
Near Limit in Some AreasSource: Industrial manufacturing, electronics production, firefighting foam
Health Effects: Increased cholesterol, changes in liver function, decreased vaccine response in children, increased risk of certain cancers
San Jose Levels: Varies by area; some groundwater sources show 3.2-3.8 ppt combined PFOA/PFOS
EPA Limit: 4 ppt for PFOA and PFOS
Lead
Below LimitSource: Lead service lines, lead solder in plumbing, and older fixtures in pre-1986 buildings
Health Effects: Developmental delays in children, learning disabilities, reduced IQ, kidney problems, high blood pressure
San Jose Levels: Average 4.2 ppb (90th percentile), with approximately 5% of samples exceeding the EPA action level
EPA Limit: Action level 15 ppb, but no safe level exists
Perchlorate
Below Limit, But PresentSource: Industrial manufacturing, aerospace operations, historical electronics production
Health Effects: Thyroid disruption, particularly concerning for pregnant women and children
San Jose Levels: 2-4 ppb in some groundwater sources, primarily in North San Jose
California Limit: 6 ppb
Hard Water Minerals
Not a Health ConcernSource: Natural mineral content in groundwater sources
Health Effects: No direct health concerns, but can cause dry skin, hair issues, and appliance/plumbing damage
San Jose Levels: 11.3 grains per gallon (193 mg/L), considered "hard" to "very hard"
EPA Limit: Not regulated (aesthetic concern only)
Neighborhood Variations
Water quality can vary significantly across San Jose's neighborhoods, primarily due to different water sources and infrastructure age.
Water Quality by Area
| Neighborhood/Area | Risk Level | Primary Water Source | Buildings Pre-1986 | Notable Concerns |
|---|---|---|---|---|
| North San Jose/Alviso | High | Groundwater | 45% | PFAS, Perchlorate, Industrial Legacy |
| Downtown/Japantown | High | Mixed | 78% | Lead, Aging Infrastructure |
| East San Jose | Medium | Groundwater/Surface Mix | 62% | Lead, Hard Water |
| Willow Glen | Medium | Surface Water | 58% | Lead, Hard Water |
| Cambrian/Campbell Border | Medium | Surface Water | 47% | Hard Water, Seasonal Variations |
| Almaden Valley | Low | Reservoir Water | 25% | Hard Water Only |
Data based on San Jose Water and Valley Water sampling and U.S. Census housing statistics.
Recommended Action Steps
Based on San Jose's water quality data, we recommend these actions to protect yourself and your family.
Identify Your Water Source
Since San Jose's water comes from multiple sources, contact your water provider to determine your specific source. San Jose Water Company and Valley Water both provide maps showing which areas receive groundwater versus surface water.
Check Your Water SourceTest Your Water If in a High-Risk Area
If you live in North San Jose, Alviso, Downtown, or other areas with industrial history or older infrastructure, consider testing your water for PFAS, lead, and other contaminants specific to your neighborhood.
Water Testing ResourcesConsider Advanced Filtration for PFAS
If you're in an area with known PFAS contamination (particularly North San Jose and Alviso), consider a reverse osmosis system or a filter certified to NSF/ANSI P473 standard for PFAS reduction. These provide the highest level of protection against these concerning chemicals.
Address Hard Water Issues
Install a water softener to mitigate San Jose's hard water, which can extend the life of appliances and plumbing while improving soap effectiveness. This is particularly important in areas receiving primarily groundwater.
Run Water Before Use in Older Homes
If your home was built before 1986, run cold water for 30-60 seconds before using it for drinking or cooking, especially first thing in the morning or after being away from home for several hours.
Stay Informed During Drought Periods
During drought conditions, contaminant concentrations can increase in water supplies. Pay attention to water quality notices and consider more rigorous filtration during extended dry periods.
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