San Luis Obispo County, California
34 ZIP codes · Avg score 71/100 · Grade B · Updated 2026-06-04
Unlike many counties its size, San Luis Obispo County keeps violation rates low — all 34 ZIP codes score at or above the state average for tap water safety, with no systemic concerns flagged in the current data set.
How San Luis Obispo County Compares
How San Luis Obispo County Compares
San Luis Obispo County scores 2 points below the California state average (73/100) and 3 points above the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-04
ZIP Code Risk Map
Water Quality Map: San Luis Obispo County, California
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Key Risk Factors
Health risk index: 11.3 (asthma 9.9%, diabetes 10%)
Estimated additional annual cost per homeowner: $1,150, driven primarily by flood
Infrastructure: 0.322% avg pipe failure probability, 9% of ZIPs at high risk
Violation History (2021–2025)
→ Stable trendEPA violation counts by year across San Luis Obispo County water systems. Health-based shown in red, total in blue.
Peak year: 2023 with 34 violations. Past 5 years: 114 total (114 health-based).
Source: EPA SDWIS historical violations. Data may lag 6–12 months for the most recent year.
County Health Indicators vs National Average
Black markers indicate national averages. Source: CDC PLACES, Census ACS.
Infrastructure Overview
Sources: Census ACS (housing age), EPA SDWIS (infrastructure risk model), state bridge inspection data.
Compound Risk Breakdown
Estimated additional annual cost per homeowner: $1,150
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Water Safety Affordability
How much it costs to fix water issues relative to home values in San Luis Obispo County
Remediation costs are relatively manageable for most homeowners in San Luis Obispo County, representing a small fraction of property value.
Remediation includes water filtration, lead abatement, radon mitigation, and flood protection where applicable. Source: Census ACS, EPA SDWIS.
Health Outcomes vs National Average
CDC PLACES data for San Luis Obispo County residents
Black markers = national averages. Red = above national avg. Green = below. Source: CDC PLACES, Census ACS.
Water Systems with Most Violations
Top 5 systems in San Luis Obispo County ranked by EPA violation count.
| # | Water System | Population | Violations |
|---|---|---|---|
| 1 | City of Grover Beach Public Works Department | 12,701 | 45 |
| 2 | Bassi Ranch Mutual Water Company | 85 | 44 |
| 3 | Rim Rock Water Company | 55 | 44 |
| 4 | Slocsa #10a - Cayucos | 1,200 | 17 |
| 5 | San Luis Obispo Water Department | 47,788 | 16 |
42 total water systems serve San Luis Obispo County.
All ZIP Codes in San Luis Obispo County
34 ZIP codes tracked in San Luis Obispo County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 93412 | Los Osos | 83 | B | 0 | — |
| 2 | 93403 | San Luis Obispo | 82 | B | 2 (1 health) | — |
| 3 | 93406 | San Luis Obispo | 82 | B | 2 (1 health) | — |
| 4 | 93407 | San Luis Obispo | 82 | B | 2 (1 health) | — |
| 5 | 93408 | San Luis Obispo | 82 | B | 2 (1 health) | — |
| 6 | 93409 | San Luis Obispo | 82 | B | 2 (1 health) | — |
| 7 | 93410 | San Luis Obispo | 82 | B | 2 (1 health) | — |
| 8 | 93424 | Avila Beach | 82 | B | 1 (1 health) | $1180K |
| 9 | 93443 | Morro Bay | 82 | B | 1 (1 health) | — |
| 10 | 93421 | Arroyo Grande | 81 | B | 2 | — |
| 11 | 93402 | Los Osos | 78 | B | 0 | $729K |
| 12 | 93423 | Atascadero | 78 | B | 3 | — |
| 13 | 93430 | Cayucos | 78 | B | 0 | $965K |
| 14 | 93444 | Nipomo | 78 | B | 0 | $746K |
| 15 | 93420 | Arroyo Grande | 76 | B | 2 | $872K |
| 16 | 93428 | Cambria | 76 | B | 1 (1 health) | $870K |
| 17 | 93448 | Pismo Beach | 76 | B | 4 (3 health) | — |
| 18 | 93422 | Atascadero | 74 | B | 3 | $692K |
| 19 | 93401 | San Luis Obispo | 72 | B | 2 (1 health) | $944K |
| 20 | 93405 | San Luis Obispo | 72 | B | 2 (1 health) | $898K |
| 21 | 93442 | Morro Bay | 72 | B | 1 (1 health) | $871K |
| 22 | 93449 | Pismo Beach | 72 | B | 4 (3 health) | $993K |
| 23 | 93465 | Templeton | 72 | B | 0 | $875K |
| 24 | 93475 | Oceano | 72 | B | 1 | — |
| 25 | 93445 | Oceano | 70 | B | 1 | $538K |
| 26 | 93433 | Grover Beach | 58 | C | 22 (19 health) | $692K |
| 27 | 93432 | Creston | 53 | D | 0 | $900K |
| 28 | 93435 | Harmony | 53 | D | 0 | — |
| 29 | 93461 | Shandon | 53 | D | 0 | $455K |
| 30 | 93446 | Paso Robles | 51 | D | 8 (8 health) | $661K |
| 31 | 93453 | Santa Margarita | 50 | D | 0 | $720K |
| 32 | 93483 | Grover Beach | 50 | D | 22 (19 health) | — |
| 33 | 93447 | Paso Robles | 48 | D | 8 (8 health) | — |
| 34 | 93452 | San Simeon | 48 | D | 2 (2 health) | $277K |
Recommended Buyer Guides for San Luis Obispo County
Strictly editorial — no paid placements influence which guides appear; the selection draws on NSF certifications and EPA detection records for water systems serving this county.
- Best Water Filters for Lead — Lead above EPA action level in 1 ZIP code
- Best Under-Sink Reverse Osmosis Systems — Multi-contaminant removal at the kitchen tap
- Best Sump Pumps — Flood is the top compound risk factor
- Best Mold Test Kits — Flood-driven moisture and mold risk
Deep Dive Reports
Detailed analysis for San Luis Obispo County, California
Overview
San Luis Obispo County in California covers 34 ZIP codes with an average Home Safety Score of B (71/100).
25 of 34 ZIP codes have recorded EPA violations. 74 health-based violations have been documented.
← Back to California water quality report
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Home values: U.S. Census Bureau ACS (median estimates by ZCTA)
Updated daily.