Skip to main content
WaterSafeCheck

ZIP Code 91788 Water Quality Report

Walnut, CA · Los Angeles County County

Safety Score
B

Water Safety Grade

Good — Minor issues on record

Health Violations

0

Total Violations

0

Lead Risk

N/A

Contaminants

0

About Tap Water in ZIP Code 91788

Tap water in ZIP code 91788 (Walnut, CA) meets all federal safety standards and earns a solid B grade (score: 83/100). Served by Walnut Valley Water District, the water system has maintained general compliance with EPA Safe Drinking Water Act regulations, with only minor issues on record.

Water System

Walnut Valley Water District

EPA ID: CA1910234

Water Source

Surface Water

Population Served

100,941 residents

County

Los Angeles County County, California

🧪

Lead Levels in ZIP 91788

EPA action level: 15 ppb | Public health goal: 0 ppb

Lead Level: 2.7 ppb — Very Low

The 90th percentile lead level in 91788 is 2.7 ppb, well below the EPA action level of 15 ppb. While this is a reassuring result, the EPA's public health goal for lead is actually zero — no amount of lead is considered completely safe, particularly for children under 6 and pregnant women. Running your tap for 30 seconds before use and using a certified NSF/ANSI 53 filter adds an extra layer of protection.
Lead Level (90th percentile)
2.70 ppb (0.0027 mg/L)
Lead Exposure Risk Rating
Unknown
Note: Lead levels above are the 90th percentile from EPA monitoring — meaning 90% of samples were at or below this level. Even "undetected" tap water lead doesn't account for lead leaching from home plumbing. If your home was built before 1986, individual tap testing is recommended.
📋

Violation History

Past 5 years — EPA SDWIS data

Walnut Valley Water District has recorded zero violations in the EPA compliance database over the past 5 years — a strong indicator of consistent regulatory compliance and careful monitoring.

Total Violations (5 yr)
0
Health-Based Violations
0
Unresolved Violations
0
Boil Water Advisories
0
Compliance Risk
Low

Regulatory compliance risk for Walnut Valley Water District is rated Low — indicating a consistent track record of meeting EPA reporting and treatment requirements.

⚗️

Contaminants Detected

Contaminants with health-based violations on record

No health-based contaminant violations are on record for ZIP code 91788. This means EPA monitoring has not found levels of regulated contaminants exceeding the Maximum Contaminant Levels (MCLs) set under the Safe Drinking Water Act — a positive indicator of water quality compliance.

🌊

Water Source & Environmental Factors

Surface Water

This system draws water from lakes, rivers, or reservoirs. Surface water is treated to remove sediment, microorganisms, and chemical contaminants before reaching taps.

Water Source Type
Surface Water
CCR Source Classification
Surface Water (Purchased)
EPA Radon Zone

Moderate potential

Zone 2

EPA Radon Zone 2 — moderate radon potential. The EPA recommends testing your home regardless of zone designation.

🛡 What Should You Do? — ZIP 91788 Recommendations

  • ✓ Run cold water for 30 seconds each morning before use — especially if pipes are old
  • ✓ Request your annual Consumer Confidence Report from Walnut Valley Water District
  • ✓ If your home was built before 1986, consider testing your own tap for lead
  • ✓ Use a pitcher filter (NSF/ANSI 42 certified) for improved taste

Frequently Asked Questions — ZIP 91788 Water Quality

Is tap water safe to drink in ZIP code 91788?+
Yes — tap water in 91788 (Walnut, CA) currently meets all federal EPA standards with a water safety grade of B. No health-based violations are on record in the past 5 years. You can drink your tap water with confidence, though running the tap for 30 seconds in the morning is always a good practice.
What is the lead level in 91788 tap water?+
The 90th percentile lead level in 91788 is 2.7 ppb (parts per billion). The EPA action level is 15 ppb. This is a low level, well below the EPA action level of 15 ppb.
Who provides tap water to 91788?+
Tap water in ZIP code 91788 is provided by Walnut Valley Water District (EPA ID: CA1910234). This system serves approximately 100,941 residents. You can contact them directly for Consumer Confidence Reports, current advisories, and billing information.
What is the water source for 91788?+
ZIP code 91788 is served by surface water. Surface water systems draw from rivers, lakes, or reservoirs and must meet strict EPA treatment requirements including filtration and disinfection.
Does 91788 have any active water quality violations?+
No active violations are on record for ZIP code 91788. EPA data shows this water system is currently in compliance with Safe Drinking Water Act standards.
How do I get a copy of my water quality report for 91788?+
Your water utility — Walnut Valley Water District — is required by law to send you an annual Consumer Confidence Report (CCR) by July 1 each year. You can also request it directly from the utility or find it online by searching "Walnut Valley Water District Consumer Confidence Report." The EPA's ECHO database also has historical compliance data.
What water filter should I use in 91788?+
The right filter depends on what contaminants are present. For lead, look for a filter certified to NSF/ANSI Standard 53. For chlorine byproducts (like THMs), NSF/ANSI 42 filters work well. For a broad range of contaminants including PFAS, look for NSF/ANSI 58 (reverse osmosis) systems. For ZIP code 91788, with a clean compliance record, a standard carbon block filter meeting NSF/ANSI 42 is a good choice for taste and as a precaution.
Is 91788 tap water safe for babies and infants?+
Infants are especially vulnerable to lead, nitrates, and microbial contaminants in drinking water. Current EPA data for 91788 shows a lead level of 2.7 ppb — below the action level, but as an extra precaution, run your tap for 30 seconds before use and consider a certified lead filter for infant formula. Always consult your pediatrician for guidance specific to your child's health.

Data Sources & Methodology

Water quality data for ZIP code 91788 is compiled from the EPA Safe Drinking Water Information System (SDWIS), EPA ECHO enforcement database, UCMR5 unregulated contaminant monitoring, and Consumer Confidence Reports filed by Walnut Valley Water District. Safety scores are composite metrics derived from violation history, lead levels, enforcement actions, and infrastructure risk indicators. Data reflects a 5-year monitoring window. Last dataset update: 2024. View EPA source data →