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WaterSafeCheck
Official EPA SDWIS Verified ReportWater Quality & Testing GuideStatus: Normal Operations

ZIP Code 95370 Water Quality & Testing Report

Sonora, CA · Tuolumne County County · Updated for 2026

Quick EPA Verified Answer

Is Tap Water Safe to Drink in ZIP 95370 (Sonora, CA)?

Yes, tap water in ZIP code 95370 (Sonora, CA) is safe to drink under EPA Safe Drinking Water Act standards. Supplied by Tud - Upper Basin Water System, the area earns an EPA Safety Grade of B (70/100) with 0 health violations, 8.1 ppb lead, and hard (123 mg/L / 7.2 GPG) water.

Safety Score
B

Water Safety Grade

Good — Minor issues on record

Health Violations

0

Total Violations

1

Lead Risk

High

Contaminants

0

⚠

Active Water Quality Issues Detected

EPA records show 0 unresolved violation. Contact Tud - Upper Basin Water System for current status.

About Tap Water in ZIP Code 95370

Tap water in ZIP code 95370 (Sonora, CA) is distributed by Tud - Upper Basin Water System (EPA ID: CA5510012), serving approximately 13,280 residents. Based on EPA Safe Drinking Water Act compliance records, this system receives a water safety grade of B with a composite quality score of 70/100.

Water System

Tud - Upper Basin Water System

EPA ID: CA5510012

Water Source

Surface Water

Population Served

13,280 residents

County

Tuolumne County County, California

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Lead Levels in ZIP 95370

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

Lead Level: 8.1 ppb — Moderate

The 90th percentile lead level in 95370 is 8.1 ppb. This is below the EPA action level of 15 ppb, but above ideal health goals. Consider a certified lead-reducing filter.

Lead exposure risk in 95370 is rated High. EPA models estimate a 56% exposure probability based on housing and infrastructure age.

Lead Level (90th percentile)
8.10 ppb (0.0081 mg/L)
Lead Exposure Risk Rating
High
Lead Exposure Probability

EPA model estimate based on housing age and infrastructure

56%
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.
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Water Hardness & Mineral Content

Grains per gallon (GPG) & Parts per million (PPM / mg/L)

Classification: Hard7.2 GPG · 123 mg/L

Water in ZIP 95370 is Hard (123 mg/L / 7.2 GPG). Residents may notice white mineral spots on glassware, reduced soap efficiency, and mineral scale on faucets and showerheads.

Recommendation: An ion-exchange water softener or descaler is recommended to prolong the life of water heaters, dishwashers, and plumbing.
Hardness (GPG)

Grains per gallon

7.2 GPG
Hardness (PPM / mg/L)

Parts per million CaCO3

123 mg/L
Appliance Scaling Risk
High / Severe

Official EPA SDWIS Database Entry

Utility: Tud - Upper Basin Water System · PWSID: CA5510012

Verify on EPA.gov
📋

Violation History

Past 5 years — EPA SDWIS data

Tud - Upper Basin Water System has recorded 1 violation, but none are health-based (e.g., administrative or monitoring infractions).

Total Violations (5 yr)
1
Health-Based Violations
0
Unresolved Violations
0
Boil Water Advisories
0
Compliance Risk
Low

Regulatory compliance risk for this utility is rated Low 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 95370 under the Safe Drinking Water Act.

⚖ Enforcement Actions

EPA or state regulators have issued 6 enforcement actions to address compliance lapses.
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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
EPA Radon Zone

Moderate potential

Zone 2
Annual Flood Risk Cost

Estimated annual flood-related costs per property

$0
Energy Burden

% of household income spent on energy — indicator of older infrastructure

5.03%

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

Water Quality Testing in ZIP 95370

Tap Water & Well Testing Recommendations

Residents in ZIP code 95370 served by Tud - Upper Basin Water System 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.
Certified Lab Testing: Always use an EPA-certified drinking water laboratory in CA for formal legal or real estate compliance testing.

🛡 What Should You Do? — ZIP 95370 Recommendations

  • ✓ Run cold water for 30 seconds each morning before use — especially if pipes are old
  • ✓ Request your annual Consumer Confidence Report from Tud - Upper Basin Water System
  • ✓ 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

Recommended Taste & Safety Filter:

🚰

NSF/ANSI 53 Certified Pitcher Filter

Best for removing aesthetic chlorine, odors, and low-level heavy metals.

Filter Selection Guide →

Frequently Asked Questions — ZIP 95370 Water Quality

Is tap water safe to drink in ZIP code 95370?+
Yes — tap water in 95370 (Sonora, CA) meets EPA standards with a water safety grade of B. No health-based violations are on record in the past 5 years.
How do I get my water tested in ZIP 95370 (Sonora, CA)?+
To test water quality in ZIP 95370, you can order a certified drinking water test kit or send water samples to an EPA/NELAP certified laboratory in CA. Certified testing checks for lead, coliform bacteria, nitrates, hardness, and PFAS that standard test strips miss. Contact California State Water Resources Control Board for a list of certified regional labs.
How hard is the tap water in 95370?+
Tap water in 95370 is classified as Hard with an estimated mineral hardness of 123 mg/L (7.2 GPG). An ion-exchange water softener or descaler is recommended to prolong the life of water heaters, dishwashers, and plumbing.
Should I test private well water in 95370?+
Yes. Unlike municipal systems, private wells in 95370 are not regulated by the EPA or local utilities. Private well owners should test their water annually for coliform bacteria and nitrates, and every 3 to 5 years for heavy metals (lead, arsenic) and volatile organic compounds.
What is the lead level in 95370 tap water?+
The 90th percentile lead level in 95370 is 8.1 ppb. The EPA action level is 15 ppb. This is below the EPA action level.
Is there an active boil water notice in 95370?+
There are currently no active boil water advisories on record for 95370. Water treatment systems are operating within normal parameters.
Who provides tap water to 95370?+
Tap water in ZIP code 95370 is provided by Tud - Upper Basin Water System (EPA ID: CA5510012), serving approximately 13,280 residents.
What water filter should I use in 95370?+
Based on water metrics for 95370, we recommend Lead & Microplastic Filter. Look for certifications such as NSF/ANSI 53 (Lead Reduction), NSF/ANSI 42 (Particulate/Taste).

Data Sources & Methodology

Water quality data for ZIP code 95370 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 Tud - Upper Basin Water System. 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 →