ZipCheckup grade for 91789: C.
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Walnut, CA (91789): PFAS Detected in Mapped Water Systems - 58/100
EPA data combined for 6 water systems mapped to this ZIP (largest mapped system: Walnut Valley Water District)
EPA records for the water systems mapped to 91789 in Walnut, CA contain 1 recorded violations for inclusive record years 2021 through 2026, all mapped systems combined; 0 are marked health-based.
Data source: U.S. Environmental Protection Agency (EPA) SDWIS
At a Glance
- Water EPA records for water systems mapped to this ZIP show 1 violation (non-health) (since 2021).
- Lead The reported 90th-percentile lead result is below the laboratory reporting limit, not a measured zero; EPA's health goal for lead is zero.
- PFAS At least one PFAS result is above an EPA MCL value (UCMR5 sampling; MCL compliance required from 2029).
- Radon EPA Zone 2 - county-level radon potential, not a home measurement.
- Flood 7 cumulative NFIP claim records. Claim evidence is historical, not current map coverage.
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Read the card below - it documents the sole critical-level finding on file for Walnut (91789), with the high-priority tier of the same safety record returning zero results.
Score Breakdown
Overall Home Safety Score: 58/100
This is the published model score. Component and domain values are shown independently; they are not added together on this page.
Canonical components
Required domains
Coverage: 4 of 4 components and 3 of 3 domains observed.
Model 4.0.0; series home-safety-v4-cross-vertical.
Safety & Health (8) HIGH
Your Water System
ZIP code 91789 in Walnut, California is mapped to the water system Walnut Valley Water District (EPA ID: CA1910234). This system provides water to approximately 100,941 people from surface water sources.
There are 6 community water systems serving this area.
Water Systems Serving This Area
| System Name | EPA ID | Population | Source |
|---|---|---|---|
| Walnut Valley Water District | CA1910234 | 100,941 | Surface water |
| Suburban Water Systems-san Jose | CA1910205 | 168,843 | Surface water |
| Gswc-san Dimas | CA1910142 | 56,538 | Surface water |
| Pomona - City, Water Department | CA1910126 | 151,713 | Surface water |
| Rowland Water District | CA1910194 | 56,100 | Surface water |
Other Water Quality Reports in California
- 90001 (Los Angeles)
- 90002 (Los Angeles)
- 90003 (Los Angeles)
- 90004 (Los Angeles)
- 90005 (Los Angeles)
- 90006 (Los Angeles)
- 90007 (Los Angeles)
- 90008 (Los Angeles)
- 90009 (Los Angeles)
- 90010 (Los Angeles)
- 90011 (Los Angeles)
- 90012 (Los Angeles)
- 90013 (Los Angeles)
- 90014 (Los Angeles)
- 90015 (Los Angeles)
- 90016 (Los Angeles)
- 90017 (Los Angeles)
- 90018 (Los Angeles)
- 90019 (Los Angeles)
- 90020 (Los Angeles)
Nearby Water Quality Reports
- 91795 (Walnut) - <1 mi
- 91788 (Walnut) - <1 mi
- 91792 (West Covina) - 2 mi - 1 violation recorded for mapped water systems
- 91765 (Diamond Bar) - 3 mi
- 91748 (Rowland Heights) - 3 mi
- 91791 (West Covina) - 4 mi - 1 violation recorded for mapped water systems
- 91744 (La Puente) - 5 mi - 1 violation recorded for mapped water systems
- 91723 (Covina) - 5 mi
- 91724 (Covina) - 5 mi - 1 violation recorded for mapped water systems
- 91747 (La Puente) - 5 mi
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View available EPA compliance records for Walnut Valley Water District (CA1910234) on EPA.gov.
3 of the top compounds applied across the surrounding county in USGS pesticide-use estimates appear on EPA drinking-water monitoring lists. See the agricultural pesticide-use section.
PFAS Contamination Detected
PFAS ("forever chemicals") have been reported in samples from water systems associated with ZIP code 91789. One or more compound results are above the level of a federal PFAS MCL with compliance required from 2029.
Detected compounds: PFOS, PFOA, PFBA, PFPeA, PFHxS, PFHxA, PFBS.
Highest measured level: 0.023 µg/L
Reverse osmosis (RO) and activated carbon block filters can reduce PFAS at the tap. Certifications list the compounds covered: an NSF/ANSI 53 or 58 claim for PFOA/PFOS does not cover every PFAS, so check that the product lists the compounds detected here.
Environmental Hazards (11) CRITICAL
Home & Infrastructure (6) MODERATE
Cost & Community (9) HIGH
CPSC product recall notices
These national notices are not matched to this ZIP code or water system.
Protect Your Home in Walnut
Based on local data for ZIP 91789, these services may benefit homeowners in your area.
Based on local data for your area. Use the tools below to explore your options.
Home & Flood Insurance
The ZIP code for this report in Walnut has 7 FEMA flood claims on record. Standard homeowner policies don't cover flood damage - make sure you're protected.
Typical cost: Flood insurance: premiums vary by property and flood zone; request a quote
Check Your Flood Zone (Free)FEMA flood map lookup - see if your property is in a flood zone
Free tip: Check your FEMA flood zone at msc.fema.gov (free lookup)
Gutter Installation & Repair
The median home in 91789 was built around 1987. Aging gutters can cause foundation damage, basement flooding, and mold - a professional assessment can prevent costly repairs.
Typical cost: Gutter installation: typically $1,000–$2,500 for a standard home
Estimate Your Home Maintenance CostsRoofing Inspection & Repair
Active weather alerts in California increase the risk of roof damage from hail and high winds. A professional inspection can identify vulnerabilities.
Typical cost: Roof inspection: typically $75–$300; repairs $300–$1,500
Estimate Your Home Insurance NeedsService recommendations are based on public data for this ZIP code (FEMA, Census ACS, NWS). Actual needs vary by property. By calling, your information will be shared with an independent service provider. ZipCheckup may receive compensation. Cost estimates are approximate and vary by property, condition, and contractor.
Frequently Asked Questions
Is the tap water in 91789 safe to drink?
EPA SDWIS records 1 violation since 2021 across the water systems mapped to ZIP 91789 (primary system: Walnut Valley Water District), including 0 health-based. The violation table above shows which system each record belongs to. ZipCheckup last updated this page in July 2026. The federal source release date is unavailable, so that month is not presented as source currency.
Where does 91789's water come from?
The recorded water source for Walnut Valley Water District, a system mapped to ZIP code 91789, is Surface water. This system serves approximately 100,941 people.
How does Walnut water compare to the national average?
Walnut's Home Safety Score ranks lower than 85% of U.S. ZIP codes, and lower than 95% of ZIP codes within California.
How can I get my water tested in Walnut?
If Walnut Valley Water District supplies your home, contact it for its Consumer Confidence Report; otherwise contact the water utility that serves your address, or hire a certified lab for independent home water testing. The EPA recommends annual testing if you use a private well.
What is the radon risk for 91789?
91789 is mapped to a county in EPA Radon Zone 2 (moderate county-level radon potential; EPA recommends testing every home), located in Los Angeles County. EPA radon zones range from Zone 1 (highest county-level potential) to Zone 3 (lowest). Testing your home is recommended regardless of zone.
Are there PFAS (forever chemicals) in 91789's water?
Yes, PFAS have been detected in samples from water systems mapped to 91789. One or more PFAS results are above the level of a federal PFAS MCL with compliance required from 2029. Reverse osmosis and activated carbon filters certified to NSF/ANSI 53 or 58 specifically for PFOA/PFOS reduction can reduce PFAS.
What does the NFIP claim history show for ZIP 91789?
FEMA records contain 7 flood insurance claims filed in ZIP code 91789; the recorded rated-zone value (the most frequent one if there are several claims) is A, which is claims evidence and may differ from the current FEMA map zone for a property. Claim records do not establish current property risk. Review FEMA's map for the specific property.
How to cite this page
ZipCheckup. (2026). Walnut, CA (91789): PFAS Detected in Mapped Water Systems - 58/100. https://zipcheckup.com/report/91789/
@misc{zipcheckup-report-91789,
author = {{ZipCheckup}},
title = {{Walnut, CA (91789): PFAS Detected in Mapped Water Systems - 58/100}},
year = {2026},
url = {https://zipcheckup.com/report/91789/}
}
Page version: October 2026.
Nearby ZIP Code Reports
Water quality comparison for ZIP codes near 91789
| ZIP Code | City, State | Distance | Grade | Violations |
|---|---|---|---|---|
| 91795 | Walnut, CA | <1 mi | N/A | 0 |
| 91788 | Walnut, CA | <1 mi | N/A | 0 |
| 91792 | West Covina, CA | 2.5 mi | B | 1 |
| 91765 | Diamond Bar, CA | 2.7 mi | B | 0 |
| 91748 | Rowland Heights, CA | 3.5 mi | B | 0 |
| 91791 | West Covina, CA | 4.1 mi | C | 1 |
| 91744 | La Puente, CA | 4.8 mi | B | 1 |
| 91723 | Covina, CA | 5.0 mi | C | 0 |
| 91724 | Covina, CA | 5.2 mi | C | 1 |
| 91747 | La Puente, CA | 5.4 mi | N/A | 0 |
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