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Official EPA SDWIS Verified ReportWater Quality & Testing GuideHistorical Record: No Recorded SDWIS Violations

ZIP Code 93403 Water Quality & Testing Report

San Luis Obispo, CA · San Luis Obispo County County · Updated for 2026

Sahajul HaqueCompiled & verified by Sahajul Haque from official EPA SDWIS records
Public Health & Medical Notice: Drinking water quality data on this page reflects historical compliance records submitted under the Safe Drinking Water Act. This information does not constitute medical advice or a real-time safety guarantee. If you are pregnant, nursing, preparing infant formula, or immunocompromised, consult a healthcare provider. Boiling water kills biological pathogens, but does NOT remove chemical contaminants like lead, arsenic, or PFAS.
Quick EPA Verified Answer

Is Tap Water Safe to Drink in ZIP 93403 (San Luis Obispo, CA)?

Yes, tap water in ZIP code 93403 (San Luis Obispo, CA) is safe to drink under EPA Safe Drinking Water Act standards. Supplied by San Luis Obispo Water Department, the area earns an EPA Safety Grade of B (82/100) with 1 health violations, 1.1 ppb lead, and hard (136 mg/L / 8 GPG) water.

Safety Score
B

Water Safety Grade

Good — Minor issues on record

Health Violations

1

Total Violations

2

Lead Risk

N/A

Contaminants

1

⚠

Active Water Quality Issues Detected

EPA records show 0 unresolved violation. Contact San Luis Obispo Water Department for current status.

About Tap Water in ZIP Code 93403

Tap water in ZIP code 93403 (San Luis Obispo, CA) is distributed by San Luis Obispo Water Department (EPA ID: CA4010009), serving approximately 47,788 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 82/100.

Water System

San Luis Obispo Water Department

EPA ID: CA4010009

Water Source

Surface Water

Population Served

47,788 residents

County

San Luis Obispo County County, California

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Lead Levels in ZIP 93403

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

Lead Level: 1.1 ppb — Very Low

The 90th percentile lead level in 93403 is 1.1 ppb. This meets the EPA action level of 15 ppb. Health experts recommend a target of 0 ppb for optimal safety.
Lead Level (90th percentile)
1.10 ppb (0.0011 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.
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Water Hardness & Mineral Content

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

Classification: Hard8 GPG · 136 mg/L

Water in ZIP 93403 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.

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

8 GPG
Hardness (PPM / mg/L)

Parts per million CaCO3

136 mg/L
Appliance Scaling Risk
High / Severe

Official EPA SDWIS Database Entry

Utility: San Luis Obispo Water Department · PWSID: CA4010009

Verify on EPA.gov
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Violation History

Past 5 years — EPA SDWIS data

San Luis Obispo Water Department has recorded 1 health-based violation out of 2 total violations over the past 5 years.

Total Violations (5 yr)
2
Health-Based Violations
1
Unresolved Violations
0
Boil Water Advisories
0
Compliance Risk
Moderate

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

EPA records identify 1 contaminant with health-based violations in the past 5 years: Consumer Confidence Report Rule.

Consumer Confidence Report Rule

⚖ Enforcement Actions

EPA or state regulators have issued 4 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
CCR Source Classification
Surface Water
EPA Radon Zone

Moderate potential

Zone 2

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

Water Quality Testing in ZIP 93403

Tap Water & Well Testing Recommendations

Residents in ZIP code 93403 served by San Luis Obispo Water Department 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 93403 Recommendations

  • ✓ Run cold water for 30 seconds each morning before use — especially if pipes are old
  • ✓ Request your annual Consumer Confidence Report from San Luis Obispo Water Department
  • ✓ 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 93403 Water Quality

Is tap water safe to drink in ZIP code 93403?+
Yes — tap water in 93403 (San Luis Obispo, 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 93403 (San Luis Obispo, CA)?+
To test water quality in ZIP 93403, 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 93403?+
Tap water in 93403 is classified as Hard with an estimated mineral hardness of 136 mg/L (8 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 93403?+
Yes. Unlike municipal systems, private wells in 93403 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 93403 tap water?+
The 90th percentile lead level in 93403 is 1.1 ppb. The EPA action level is 15 ppb. This is below the EPA action level.
Is there an active boil water notice in 93403?+
There are currently no active boil water advisories on record for 93403. Water treatment systems are operating within normal parameters.
Who provides tap water to 93403?+
Tap water in ZIP code 93403 is provided by San Luis Obispo Water Department (EPA ID: CA4010009), serving approximately 47,788 residents.
What water filter should I use in 93403?+
Based on water metrics for 93403, we recommend Reverse Osmosis (PFAS & Lead). Look for certifications such as NSF/ANSI 53 (Chemical Contaminants), NSF/ANSI 42 (Aesthetic Effects).

Data Sources & Methodology

Water quality data for ZIP code 93403 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 San Luis Obispo Water Department. 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 →