Palo Alto, CA Water Safety: 78/100 (2026)
6 ZIP codes · 5 water systems · Updated 2026-06-03
Based on current monitoring, Palo Alto holds an above-average drinking water safety record for CA — violations are infrequent and typically minor when they do appear.
How Palo Alto Compares
Data: EPA SDWIS Last verified: 2026-06-03
Water Quality Map: Palo Alto, CA
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Score Distribution
Distribution of water safety grades across Palo Alto.
Palo Alto Water: The Quick Version
- Average lead level: 0.0011 mg/L.
- Homes built before 1986: 67% — older plumbing may contain lead solder.
- Estimated remediation: $1,383 per household.
- CDC health risk index: 9.01.
Water Systems Serving Palo Alto
Federal drinking water records identify 5 systems in Palo Alto, CA. The leading 3 providers serve the largest share of residential connections, each operating as a separate entity with its own rate authority, infrastructure management, and EPA compliance obligations — so service conditions are not uniform city-wide.
Overview
We track water quality and home safety data for 6 ZIP codes in Palo Alto, California (population ~96,507), covering 5 community water systems serving approximately 209,736 people region-wide.
No EPA violations recorded across any ZIP codes in Palo Alto — an excellent indicator of water quality.
Home Safety Score
Average Home Safety Score for Palo Alto: B (78/100)
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
Palo Alto water systems draw from: Groundwater, Surface water.
Lead & Copper
- Average lead level (90th percentile): 0.0011 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): 6 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 |
|---|---|---|---|
| 94301 | B | City of Palo Alto | 67,231 |
| 94302 | B | City of Palo Alto | 67,231 |
| 94303 | C | City of Palo Alto | 67,231 |
| 94304 | B | City of Palo Alto | 67,231 |
| 94306 | B | City of Palo Alto | 67,231 |
| 94309 | B | City of Palo Alto | 67,231 |
All ZIP Codes in Palo Alto
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 Palo Alto
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 Palo Alto's Housing Stock?
With 67% 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
Palo Alto's housing stock is predominantly older, with a median build year of 1970 that reflects decades of construction before federal plumbing standards were tightened. The 1986 ban on lead solder and the pre-1970 era of lead service lines are both relevant benchmarks here — a significant share of the residential inventory predates one or both of those cutoffs, creating an elevated baseline for plumbing-related lead risk that aggregate water quality data may not fully reflect at the household level.
Over half of homes in Palo Alto 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.
Palo Alto: Remediation Cost in Perspective
Remediation costs in Palo Alto are small relative to typical property values — the cost-to-value ratio here is favorable.
Remediation costs in Palo Alto are relatively low compared to home values. The $650–$2,250 estimated range is a small fraction of median property value. Home values are 171% above the California average.
Protecting Children from Lead in Palo Alto
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.
67% of Palo Alto housing dates to the pre-rule era, alongside aggregate readings hovering at the federal action mark — household-level confirmation through a draw-test kit fits the local picture.
Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.
Climate-Related Water Risk for Palo Alto
The NFIP record for Palo Alto is not ambiguous: 543 claims filed and 50% of ZIP codes in FEMA-designated flood territory add up to a substantial flood exposure profile. For a water quality assessment, that profile matters because flooding doesn't just damage property — it can temporarily compromise the systems that deliver safe drinking water, from overwhelmed treatment plants to infiltrated private wells to backflow events in distribution infrastructure.
Palo Alto has a significant flood history with 543 FEMA flood insurance claims on record, averaging $9,071 per claim. With 50% of ZIP codes in FEMA-designated flood zones, flood risk is a major concern for homeowners and water quality.
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>$1,383</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 Palo Alto, CA