Williamson County, Illinois
10 ZIP codes · Avg score 72/100 · Grade B · Updated 2026-06-03
Water utilities serving Williamson County's 10 ZIP codes have built a consistent compliance record — the county's above-average grade reflects years of data showing low violation rates and no systemic health concerns.
How Williamson County Compares
How Williamson County Compares
Williamson County scores 11 points above the Illinois state average (61/100) and 4 points above the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-03
ZIP Code Risk Map
Water Quality Map: Williamson County, Illinois
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Key Risk Factors
Health risk index: 14 (asthma 10.5%, diabetes 12.4%)
Estimated additional annual cost per homeowner: $1,102, driven primarily by flood
Infrastructure: 0.423% avg pipe failure probability, 60% of ZIPs at high risk
63.3% of homes built before 1978 (lead paint era)
Violation History (2024–2025)
→ Stable trendEPA violation counts by year across Williamson County water systems. Health-based shown in red, total in blue.
Peak year: 2024 with 23 violations. Past 5 years: 26 total (26 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: $1,102
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Housing Age Distribution
28,780 housing units in Williamson 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 Williamson County
Water safety remediation is a moderate expense relative to home values. Most homeowners can address issues through staged improvements over time.
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 Williamson 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 Williamson County ranked by EPA violation count.
| # | Water System | Population | Violations |
|---|---|---|---|
| 1 | Herrin | 12,747 | 26 |
| 2 | Cambria | 1,727 | 25 |
| 3 | Carterville | 6,484 | 24 |
| 4 | Blairsville Pwd | 807 | 24 |
| 5 | Hurst | 782 | 24 |
19 total water systems serve Williamson County.
All ZIP Codes in Williamson County
10 ZIP codes tracked in Williamson County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 62915 | Cambria | 83 | B | 1 | $78K |
| 2 | 62918 | Carterville | 81 | B | 13 (2 health) | $183K |
| 3 | 62841 | Freeman Spur | 79 | B | 2 (1 health) | $64K |
| 4 | 62951 | Johnston City | 79 | B | 4 (1 health) | $90K |
| 5 | 62949 | Hurst | 77 | B | 11 (3 health) | $74K |
| 6 | 62933 | Energy | 72 | B | 0 | $139K |
| 7 | 62974 | Pittsburg | 69 | C | 4 | $162K |
| 8 | 62921 | Colp | 67 | C | 6 (1 health) | $75K |
| 9 | 62959 | Marion | 63 | C | 3 (2 health) | $166K |
| 10 | 62948 | Herrin | 48 | D | 4 | $112K |
Recommended Buyer Guides for Williamson County
Methodologically, the recommendation order reflects severity in the federal record: contaminants flagged in EPA detection records for this county outrank generic water concerns, FEMA-confirmed hazard ratings shift emergency-related categories upward, and CDC lead-exposure markers govern when lead-test kits and certified filters appear at the top of the list.
- Best Water Filters for Lead — Lead above EPA action level in 1 ZIP code
- Best Lead Paint Test Kits — 63.3% of homes built before 1978
- 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 Williamson County, Illinois
Overview
Williamson County in Illinois covers 10 ZIP codes with an average Home Safety Score of B (72/100).
9 of 10 ZIP codes have recorded EPA violations. 10 health-based violations have been documented.
← Back to Illinois 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.