ZIP Code 94558 Water Quality & Testing Report
Napa, CA · Napa County County · Updated for 2026
Compiled & verified by Sahajul Haque from official EPA SDWIS recordsIs Tap Water Safe to Drink in ZIP 94558 (Napa, CA)?
Caution / Filtration Recommended: Tap water in ZIP code 94558 (Napa, CA) has compliance concerns, earning an EPA Safety Grade of D (53/100) due to 0 health violation(s) and 102.5 ppb lead. While treated by City of Napa,, residents are advised to use an NSF/ANSI 53 certified water filter for drinking and cooking.
Water Safety Grade
Poor — Multiple violations recorded
Health Violations
0
Total Violations
1
Lead Risk
Very High
Contaminants
0
Active Water Quality Issues Detected
EPA records show 1 unresolved violation. Contact City of Napa, for current status.
About Tap Water in ZIP Code 94558
Tap water in ZIP code 94558 (Napa, CA) is distributed by City of Napa, (EPA ID: CA2810003), serving approximately 84,804 residents. Based on EPA Safe Drinking Water Act compliance records, this system receives a water safety grade of D with a composite quality score of 53/100.
Water System
City of Napa,
EPA ID: CA2810003
Water Source
Surface Water
Population Served
84,804 residents
County
Napa County County, California
Lead Levels in ZIP 94558
EPA action level: 15 ppb | Public health goal: 0 ppb
Lead Level: 102.5 ppb — EXCEEDS EPA Action Level
Lead exposure risk in 94558 is rated Very High. EPA models estimate a 79% exposure probability based on housing and infrastructure age.
EPA action level: 1.3 mg/L
EPA model estimate based on housing age and infrastructure
Water Hardness & Mineral Content
Grains per gallon (GPG) & Parts per million (PPM / mg/L)
Water in ZIP 94558 is Hard (136 mg/L / 8 GPG). Residents may notice white mineral spots on glassware, reduced soap efficiency, and mineral scale on faucets and showerheads.
Grains per gallon
Parts per million CaCO3
Official EPA SDWIS Database Entry
Utility: City of Napa, · PWSID: CA2810003
Violation History
Past 5 years — EPA SDWIS data
City of Napa, has recorded 1 violation, but none are health-based (e.g., administrative or monitoring infractions). 1 violation remains unresolved in EPA tracking records.
Regulatory compliance risk for this utility is rated Moderate based on past reporting and enforcement records.
Contaminants Detected
Contaminants with health-based violations on record
No health-based contaminant violations are on record for ZIP code 94558 under the Safe Drinking Water Act.
⚖ Enforcement Actions
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.
Lower potential
Estimated annual flood-related costs per property
% of household income spent on energy — indicator of older infrastructure
EPA Radon Zone 3 — lower radon potential, though the EPA still recommends testing all homes.
Water Quality Testing in ZIP 94558
Tap Water & Well Testing Recommendations
Residents in ZIP code 94558 served by City of Napa, can test tap water or private well systems to verify water purity. Testing detects hidden contaminants before they impact family health.
Tap Water Testing Steps
- 1.Conduct a certified lead check if your home was constructed before 1986.
- 2.Use certified lab testing kits rather than uncalibrated test strips for regulated compliance.
- 3.Sample water from both your kitchen faucet and water heater to compare line purity.
Private Well Testing Steps
- •Test for Coliform bacteria and Nitrates annually.
- •Test for heavy metals, radon, and PFAS every 3 years.
- •Send samples to a state-certified drinking water laboratory recognized by California State Water Resources Control Board.
🛡 What Should You Do? — ZIP 94558 Recommendations
Serious water quality concerns — action recommended
- 🚨 Install a certified NSF/ANSI 53 or 58 (reverse osmosis) filter immediately for drinking and cooking
- 🚨 Do not give unfiltered water to children, pregnant women, or immunocompromised individuals
- 🚨 Contact City of Napa, to request the current violation status and corrective action plan
- 🚨 Report concerns to your state environmental agency or call the EPA hotline: 1-800-426-4791
- 🚨 Consider having your home's tap water independently tested by a certified lab
Recommended Water Treatment Systems:
NSF 53 Lead Pitcher Filter
Certified to remove lead. Recommended for immediate protection.
NSF 58 Under-Sink RO System
Reverse Osmosis system certified to remove PFAS, heavy metals, and viruses.
Frequently Asked Questions — ZIP 94558 Water Quality
Is tap water safe to drink in ZIP code 94558?+
How do I get my water tested in ZIP 94558 (Napa, CA)?+
How hard is the tap water in 94558?+
Should I test private well water in 94558?+
What is the lead level in 94558 tap water?+
Is there an active boil water notice in 94558?+
Who provides tap water to 94558?+
What water filter should I use in 94558?+
Data Sources & Methodology
Water quality data for ZIP code 94558 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 City of Napa,. 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 →