Is Los Altos, CA Tap Water Safe to Drink?
Graded B, with 15 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
78.3/100
waterverge.com Los Altos, CA — Water Quality Report
Los Altos's drinking water received a grade of B (78.3 out of 100), indicating good water quality. The city's 4 water systems serve approximately 610 residents using groundwater.
Lead levels were measured at 0.0 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program.
The system has 80 violations on record, including 13 health-based violations. 15 remain unresolved.
What to know about Los Altos's water
Los Altos ranks #404 out of 694 cities in California for water quality, placing it below average in the state.
Los Altos relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff.
As a small community water system, Los Altos may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
The system has seen 8 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
Water quality score
See methodology →Is Los Altos, CA water safe to drink?
Los Altos's drinking water has significant quality concerns based on EPA testing data. With a grade of B (78.3/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 4 water systems serve approximately 610 residents using groundwater (wells).
Recent water quality updates for Los Altos
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Los Altos's water quality assessment. Grade: B (78.3/100).
Contaminants: Consumer Confidence Rule.
Federal disaster declaration (FEMA DR-3592). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-4683). Flood event — may have impacted local water infrastructure.
Contaminants: Combined Uranium, Gross Alpha, Excl. Radon and U, Lead and Copper Rule.
Contaminants: Revised Total Coliform Rule, Chlorine.
Key contaminant findings
Based on the most recent EPA sampling data for Los Altos's water supply.
Well within EPA limits.
Violation history
Los Altos's water system has 80 total violations on record, including 13 health-based violations. 15 remain unresolved. 8 violations were issued in the last 5 years.
Flood & environmental risk
Santa Clara County has experienced 8 federally declared disasters since 1982. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies. Local water sources include San Francisquito C A Stanford University, Saratoga C A Saratoga, Salt Pond A4 Nr Alviso, Coyote C Nr Alviso.
Where does Los Altos's water come from?
Los Altos's drinking water comes from groundwater (wells), supplied by 4 water systems serving approximately 610 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include San Francisquito C A Stanford University (river), Saratoga C A Saratoga (river), Salt Pond A4 Nr Alviso (lake), Coyote C Nr Alviso (river).
What Los Altos residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Los Altos's water.
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Los Altos's area has a history of flooding. After severe weather, watch for boil water advisories from your local utility.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Top industrial polluters within 10 miles of Los Altos
Industrial polluters nearby
Reported releases to surface water by facilities near Los Altos, ranked by pounds discharged annually.
Total reported releases to surface water: 4 lbs
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
NORTHROP GRUMMAN SYSTEMS CORP SUNNYVALE, CA94086 | Nickel And Nickel Compounds | 3 | 3.9 mi |
TTM TECHNOLOGIES N.A. LLC SANTA CLARA, CA95050 | Copper compounds | 1 | 8.6 mi |
US DOE SLAC NATIONAL ACCELERATOR LABORATORY MENLO PARK, CA94025 | — | — | 7.0 mi |
CSBIO MENLO PARK, CA94025 | — | — | 7.9 mi |
TE CONNECTIVY INC. REDWOOD CITY, CA94063 | — | — | 9.6 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Superfund sites within 10 miles of Los Altos
Superfund sites nearby
Federally tracked hazardous-waste sites on the EPA National Priorities List. Proximity does not necessarily indicate tap-water contamination — the connection depends on hydrology and treatment.
- SPECTRA PHYSICS INC2.9 mi
- INTEL CORP MOUNTAIN VIEW PLANT2.9 mi
- TELEDYNE SEMICONDUCTOR3.1 mi
- RAYTHEON CORP3.1 mi
- FAIRCHILD SEMICONDUCTOR CORP MOUNTAIN VIEW PLANT3.2 mi
+ 14 more sites
Source: EPA Superfund National Priorities List
Flood & disaster history
Santa Clara County has experienced 8 federally declared disasters since 1982. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 0.0 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Los Altos compares by contaminant
Explore where Los Altos ranks among all California cities for specific contaminants.
Water source & infrastructure
Where Los Altos's water comes from
Los Altos's drinking water is drawn from underground aquifers through wells.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals.
Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds.
The system is operated by private ownership and serves approximately 610 people through 4 water systems.
Water bodies near Los Altos
Los Altos is located near 4 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Los Altos
| System Name | PWSID | Population | Source |
|---|---|---|---|
| FAIRPLAY MHP | CO0147030 | 215 | GW |
| VILLA CEREZOS | CA3900596 | 200 | GW |
| GREELEY RV PARK | CO0162302 | 164 | GW |
| Puyallup River RV Park | WA5357264 | 31 | GW |
How Los Altos compares
Full California rankings →Los Altos's score of 78.3/100 is above the average of 57/100 among major California cities. It outscores 8 of 10 nearby cities.
Nearby cities
View California rankings →About Los Altos, CA
Wikipedia →Los Altos is a city in Santa Clara County, California, in the San Francisco Bay Area. The population was 31,625 according to the 2020 census.
Learn more about your water
Guides and resources related to Los Altos's water quality findings.
Explore water quality across Park
Frequently asked questions
Is Los Altos, CA tap water safe to drink?
Los Altos's water quality earned a grade of B (78.3/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #404 out of 694 cities tested in California.
What contaminants are in Los Altos's water?
Lead was measured at 0.0 ppb (90th percentile). 80 violations are on record.
How is Los Altos's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Los Altos?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Los Altos's water come from?
Los Altos's water is sourced from Groundwater. The city has 4 water systems serving approximately 610 residents.
What health violations has Los Altos's water system had?
Los Altos has 13 health-based violations on record. The most recent violation was recorded in July 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 15 violations remain unresolved.
Is Los Altos's groundwater at risk of contamination?
Los Altos uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 80 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Los Altos's water compare to other cities?
Los Altos ranks #404 out of 694 cities in California (better than 42% of state cities) and #8730 out of 15744 cities nationally (45th percentile). The grade of B reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.