San Marcos, CA: 24 Health Violations — 69/100 (2026)
4 ZIP codes · 8 water systems · Updated 2026-06-03
Based on current EPA data, San Marcos, CA reflects fair but uneven tap water safety.
How San Marcos Compares
Data: EPA SDWIS Last verified: 2026-06-03
Key Facts for San Marcos Residents
- Your city's water systems recorded 112 violations in the past 5 years.
- Average lead level: 0.0011 mg/L.
- Estimated remediation: $1,200 per household.
- CDC health risk index: 10.18.
San Marcos's Water Providers
Federal records list 8 water systems tied to San Marcos, CA. Of those, 3 are the primary providers, meaning service conditions, rate structures, and compliance histories can differ depending on where a property sits.
Overview
We track water quality and home safety data for 4 ZIP codes in San Marcos, California (population ~100,367), covering 8 community water systems serving approximately 618,979 people region-wide.
4 of 4 ZIP codes (100%) have recorded EPA violations. 24 health-based violations documented.
Home Safety Score
Average Home Safety Score for San Marcos: C (69/100)
The score combines three factors:
| Factor | What It Measures |
|---|---|
| Water Quality | EPA violations and compliance history |
| Lead Levels | 90th percentile lead concentration vs EPA action level |
| Radon Risk | EPA radon zone classification |
Water Sources
San Marcos water systems draw from: Groundwater, Surface water.
Lead & Copper
- Average lead level (90th percentile): 0.0011 mg/L (EPA action level: 0.015 mg/L)
- 0 ZIP codes exceed the EPA lead action level
Radon Risk
Dominant radon zone: Zone 3 (Low Risk)
- Zone 1 (High): 0 ZIP codes
- Zone 2 (Moderate): 0 ZIP codes
- Zone 3 (Low): 4 ZIP codes
Top Contaminants
| Contaminant | Category | Violations | ZIPs Affected |
|---|---|---|---|
| Nickel | Inorganic | 120 | 4 |
| Lead | Inorganic | 10 | 4 |
| Stage 1 DBP Rule | Treatment Technique | 5 | 4 |
| Stage 2 DBP Rule | Treatment Technique | 5 | 4 |
Areas with Most Violations
| ZIP Code | Safety Score | Violations | Health-Based | System |
|---|---|---|---|---|
| 92069 | C | 28 | 6 | Vallecitos Water District |
| 92078 | B | 28 | 6 | Vallecitos Water District |
| 92079 | C | 28 | 6 | Vallecitos Water District |
| 92096 | C | 28 | 6 | Vallecitos Water District |
All ZIP Codes in San Marcos
- 92069 [C] — 28 violations ⚠
- 92078 [B] — 28 violations ⚠
- 92079 [C] — 28 violations ⚠
- 92096 [C] — 28 violations ⚠
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Lead/copper: EPA Lead and Copper Rule sampling data
- Radon: EPA Map of Radon Zones
Updated daily.
San Marcos Community Health Snapshot
Source: CDC PLACES (County-level estimates). Water contamination can correlate with respiratory and chronic health conditions.
Compared to National Average
Vertical line = national average. ■ Above national · ■ Below national
What's in San Marcos's Water?
Based on EPA violation records. Check your ZIP code report for system-specific contaminant data.
How Remediation Costs Compare in San Marcos
In San Marcos, the equity impact of remediation is proportionally small — not the kind of financial commitment that rises to the level of a genuine planning constraint, but a minor share of what most properties here are worth.
Remediation costs in San Marcos are relatively low compared to home values. The $700–$2,400 estimated range is a small fraction of median property value. Home values are 18% above the California average.
San Marcos: Lead Risk & Vulnerable Populations
Why children are most at risk: The CDC states there is no safe level of lead exposure for children. Children under 6 absorb lead more readily than adults, and even low levels can cause developmental delays, learning difficulties, and behavioral problems.
Lead risk in San Marcos appears low overall, but individual homes may differ. Testing is the only way to confirm your water's lead content.
Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.
San Marcos: Flood History & Water Damage Risk
How does San Marcos's flood record connect to local water quality? The NFIP documents 42 claims — enough to signal recurring events — and 50% of ZIP codes carry FEMA flood zone status. That combination places flooding in the category of factors that can periodically affect water infrastructure, even if the area isn't among the highest-exposure communities in the NFIP dataset.
San Marcos has a moderate flood history with 42 FEMA claims averaging $5,328 per payout. 50% of ZIP codes fall within FEMA flood zones. Flood events can contaminate drinking water and overwhelm treatment systems.
How flooding affects water quality: Flood events can introduce sewage, agricultural runoff, and industrial chemicals into water supplies. Even after floodwaters recede, contamination can persist in wells and aging infrastructure. Flood damage can add significantly to the estimated <strong>$1,200</strong> remediation cost per household.
Residents in flood-prone areas should consider flood insurance even outside FEMA zones — over 25% of flood claims come from low-to-moderate risk areas. After any flood event, test your water before drinking.
Source: FEMA National Flood Insurance Program (NFIP) claims data, FEMA flood zone designations.
What You Can Do in San Marcos
- Test your water at home. City-level data shows averages — your tap may differ. NSF-certified test kits cost $20-40 and give results in days.
- Install a certified water filter. Filters rated for Nickel can reduce the most common contaminant found in San Marcos's water.
- Check your home's plumbing. Homes built before 1986 may have lead solder in pipes. A licensed plumber can assess your risk.
Deep Dive Reports
Detailed analysis for San Marcos, CA