Los Altos, CA Water Safety: 80/100 (2026)
3 ZIP codes · 4 water systems · Updated 2026-06-03
Public water monitoring in Los Altos shows a safety record well above the CA median — health-based violations are isolated exceptions rather than recurring patterns, the city's systems have stayed compliant across recent reporting cycles, and no cluster of recurring exceedances appears in any single service area.
How Los Altos Compares
Data: EPA SDWIS Last verified: 2026-06-03
Los Altos Water: The Quick Version
- Average lead level: 0.0023 mg/L.
- Homes built before 1986: 75% — older plumbing may contain lead solder.
- Estimated remediation: $1,700 per household.
- CDC health risk index: 9.01.
Water Systems Serving Los Altos
Los Altos, CA is covered by 3 major water utilities out of 4 federally tracked systems, each managing its own pipes, treatment processes, and EPA filings. What a household gets from the tap depends on which provider's system serves that address.
Overview
We track water quality and home safety data for 3 ZIP codes in Los Altos, California (population ~43,666), covering 4 community water systems serving approximately 165,268 people region-wide.
No EPA violations recorded across any ZIP codes in Los Altos — an excellent indicator of water quality.
Home Safety Score
Average Home Safety Score for Los Altos: B (80/100)
The score combines three factors:
| Factor | What It Measures |
|---|---|
| Water Quality | EPA violations and compliance history |
| Lead Levels | 90th percentile lead concentration vs EPA action level |
| Radon Risk | EPA radon zone classification |
Water Sources
Los Altos water systems draw from: Groundwater.
Lead & Copper
- Average lead level (90th percentile): 0.0023 mg/L (EPA action level: 0.015 mg/L)
- 0 ZIP codes exceed the EPA lead action level
Radon Risk
Dominant radon zone: Zone 2 (Moderate Risk)
- Zone 1 (High): 0 ZIP codes
- Zone 2 (Moderate): 3 ZIP codes
- Zone 3 (Low): 0 ZIP codes
The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.
Areas with No Violations
| ZIP Code | Safety Score | System | Population |
|---|---|---|---|
| 94022 | B | CITY OF PALO ALTO | 67,231 |
| 94023 | B | Villa Cerezos | 200 |
| 94024 | B | City of Mountain View | 81,501 |
All ZIP Codes in Los Altos
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Lead/copper: EPA Lead and Copper Rule sampling data
- Radon: EPA Map of Radon Zones
Updated daily.
CDC Health Data for Los Altos
Source: CDC PLACES (County-level estimates). Water contamination can correlate with respiratory and chronic health conditions.
Compared to National Average
Vertical line = national average. ■ Above national · ■ Below national
How Old Is Los Altos's Housing Stock?
With 75% of homes built before 1986, lead solder in plumbing is a potential concern. The EPA banned lead solder in 1986, but many older homes retain original plumbing.
Source: U.S. Census Bureau American Community Survey (ACS).
Housing Age Profile
Heavily weighted toward older construction, Los Altos's housing stock carries a median build year of 1964. That profile puts a majority of homes in the era when lead-soldered copper plumbing was standard practice.
Over half of homes in Los Altos were built before 1986, when lead solder was banned. Older plumbing may leach lead into drinking water, especially with corrosive water chemistry.
Source: U.S. Census Bureau ACS B25034.
Los Altos: Remediation Cost in Perspective
At current valuations, Los Altos sits in the low remediation-share tier — the equity impact of fixing documented issues is proportionally minor.
Remediation costs in Los Altos are relatively low compared to home values. The $1,100–$2,600 estimated range is a small fraction of median property value. Home values are 171% above the California average.
Protecting Children from Lead in Los Altos
Why children are most at risk: The CDC states there is no safe level of lead exposure for children. Children under 6 absorb lead more readily than adults, and even low levels can cause developmental delays, learning difficulties, and behavioral problems.
After the federal action removing lead-bearing solder from new plumbing took effect, building practice shifted — but 75% of the Los Altos inventory predates that line. With aggregate samples near or beyond 0.015 mg/L, an in-home check moves out of the optional column into the standard list.
Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.
Climate-Related Water Risk for Los Altos
Within the NFIP's national dataset, Los Altos falls in moderate-exposure territory — 35 documented incidents spanning multiple decades, with 67% of local ZIP codes sitting inside FEMA flood boundaries. That combination warrants inclusion in any thorough local water quality review.
Los Altos has a moderate flood history with 35 FEMA claims averaging $1,548 per payout. 67% of ZIP codes fall within FEMA flood zones. Flood events can contaminate drinking water and overwhelm treatment systems.
How flooding affects water quality: Flood events can introduce sewage, agricultural runoff, and industrial chemicals into water supplies. Even after floodwaters recede, contamination can persist in wells and aging infrastructure. Flood damage can add significantly to the estimated <strong>$1,700</strong> remediation cost per household.
Residents in flood-prone areas should consider flood insurance even outside FEMA zones — over 25% of flood claims come from low-to-moderate risk areas. After any flood event, test your water before drinking.
Source: FEMA National Flood Insurance Program (NFIP) claims data, FEMA flood zone designations.
Deep Dive Reports
Detailed analysis for Los Altos, CA