Walnut, CA Water Safety: 83/100 (2026)
3 ZIP codes · 6 water systems · Updated 2026-06-03
Water utilities in Walnut have maintained a consistent compliance record over recent monitoring periods — the city's above-average grade in CA reflects low violation rates and no systemic health concerns flagged in current data.
How Walnut Compares
Data: EPA SDWIS Last verified: 2026-06-03
Key Facts for Walnut Residents
- Average lead level: 0.0027 mg/L.
- Estimated remediation: $1,000 per household.
- CDC health risk index: 10.71.
Walnut's Water Providers
Across Walnut, CA, residential water comes from 3 primary utilities rather than a single consolidated provider. Each system operates independently — managing its own distribution infrastructure, rate schedules, and EPA compliance filings. Federal records track 6 water systems in the area, with these top providers accounting for the majority of residential connections.
Overview
We track water quality and home safety data for 3 ZIP codes in Walnut, California (population ~40,933), covering 6 community water systems serving approximately 532,695 people region-wide.
No EPA violations recorded across any ZIP codes in Walnut — an excellent indicator of water quality.
Home Safety Score
Average Home Safety Score for Walnut: B (83/100)
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
Walnut water systems draw from: Surface water.
Lead & Copper
- Average lead level (90th percentile): 0.0027 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 |
|---|---|---|---|
| 91788 | B | Walnut Valley Water District | 100,941 |
| 91789 | B | Walnut Valley Water District | 100,941 |
| 91795 | B | Walnut Valley Water District | 100,941 |
All ZIP Codes in Walnut
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.
Walnut Community Health Snapshot
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 Remediation Costs Compare in Walnut
At current valuations, Walnut sits in the low remediation-share tier — the equity impact of fixing documented issues is proportionally minor.
Remediation costs in Walnut are relatively low compared to home values. The $400–$1,667 estimated range is a small fraction of median property value. Home values are 27% above the California average.
Walnut: Lead Risk & Vulnerable Populations
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.
Lead risk in Walnut appears low overall, but individual homes may differ. Testing is the only way to confirm your water's lead content.
Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.
Walnut: Flood History & Water Damage Risk
How does Walnut's flood record connect to local water quality? The NFIP documents 7 claims — enough to signal recurring events — and 33% of ZIP codes carry FEMA flood zone status. That combination places flooding in the category of factors that can periodically affect water infrastructure, even if the area isn't among the highest-exposure communities in the NFIP dataset.
Walnut has a moderate flood history with 7 FEMA claims averaging $196 per payout. 33% 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>$1,000</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 Walnut, CA