St. Charles County, Missouri
13 ZIP codes · Avg score 60/100 · Grade C · Updated 2026-06-03
Water systems across St. Charles County's 13 ZIP codes produce average compliance results overall — pockets with documented violations exist, and the variation between areas makes ZIP-level lookup the most useful tool for residents here.
How St. Charles County Compares
How St. Charles County Compares
St. Charles County scores 9 points below the Missouri state average (69/100) and 8 points below the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-03
ZIP Code Risk Map
Water Quality Map: St. Charles County, Missouri
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Key Risk Factors
Health risk index: 12.2 (asthma 10.2%, diabetes 10.8%)
Estimated additional annual cost per homeowner: $1,974, driven primarily by flood
Infrastructure: 0.321% avg pipe failure probability, 25% of ZIPs at high risk
56.1% of homes built before 1978 (lead paint era)
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: $1,974
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Housing Age Distribution
134,120 housing units in St. Charles County
Source: U.S. Census Bureau ACS B25034 (Year Structure Built).
Water Safety Affordability
How much it costs to fix water issues relative to home values in St. Charles County
Remediation costs are relatively manageable for most homeowners in St. Charles 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 St. Charles 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 St. Charles County ranked by EPA violation count.
| # | Water System | Population | Violations |
|---|---|---|---|
| 1 | St Charles County Pwsd 2 | 100,587 | 17 |
| 2 | St Paul Public Water System | 1,700 | 17 |
| 3 | St Charles Company Pwsd #2 Wright City | 3,550 | 15 |
| 4 | St Charles County Pwsd 2 Warren | 1,192 | 15 |
| 5 | Ofallon Public Water System | 32,515 | 14 |
20 total water systems serve St. Charles County.
All ZIP Codes in St. Charles County
13 ZIP codes tracked in St. Charles County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 63338 | Cottleville | 83 | B | 0 | — |
| 2 | 63348 | Foristell | 79 | B | 3 | $365K |
| 3 | 63385 | Wentzville | 77 | B | 2 | $321K |
| 4 | 63368 | O Fallon | 74 | B | 6 | $328K |
| 5 | 63366 | O Fallon | 64 | C | 6 | $284K |
| 6 | 63373 | Portage Des Sioux | 63 | C | 0 | $207K |
| 7 | 63034 | Florissant | 55 | C | 0 | $234K |
| 8 | 63367 | Lake Saint Louis | 55 | C | 0 | $381K |
| 9 | 63033 | Florissant | 50 | D | 0 | $157K |
| 10 | 63138 | Saint Louis | 50 | D | 0 | $125K |
| 11 | 63031 | Florissant | 45 | D | 0 | $145K |
| 12 | 63042 | Hazelwood | 45 | D | 0 | $139K |
| 13 | 63386 | West Alton | 40 | D | 0 | $156K |
Recommended Buyer Guides for St. Charles County
Eight risk categories drive the selection — PFAS exceedance, lead above EPA action level, pre-1978 housing share, EPA Radon Zone 1, flood-top-risk, wildfire-top-risk, multi-contaminant load, and a baseline fallback — and each category maps to a specific buyer-guide track that surfaces when the county data hits its threshold for that hazard signal.
- Best Lead Paint Test Kits — 56.1% of homes built before 1978
- 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 St. Charles County, Missouri
Overview
St. Charles County in Missouri covers 13 ZIP codes with an average Home Safety Score of C (60/100).
4 of 13 ZIP codes have recorded EPA violations. All violations are monitoring/reporting type.
← Back to Missouri 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.