Johnson County, Iowa
13 ZIP codes · Avg score 56/100 · Grade C · Updated 2026-06-03
Recent monitoring in Johnson County's 13 ZIP codes shows middle-tier safety — some systems are clean; others have logged EPA violations.
How Johnson County Compares
How Johnson County Compares
Johnson County scores 3 points below the Iowa state average (59/100) and 12 points below the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-03
ZIP Code Risk Map
Water Quality Map: Johnson County, Iowa
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Key Risk Factors
Health risk index: 10.5 (asthma 9.8%, diabetes 8.8%)
Estimated additional annual cost per homeowner: $1,174, driven primarily by flood
Infrastructure: 0.379% avg pipe failure probability, 38% of ZIPs at high risk
46% of homes built before 1978 (lead paint era)
Violation History (2021–2024)
→ Stable trendEPA violation counts by year across Johnson County water systems. Health-based shown in red, total in blue.
Peak year: 2024 with 2 violations. Past 5 years: 3 total (3 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: $1,174
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Housing Age Distribution
64,226 housing units in Johnson 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 Johnson County
Remediation costs are relatively manageable for most homeowners in Johnson 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 Johnson 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 Johnson County ranked by EPA violation count.
| # | Water System | Population | Violations |
|---|---|---|---|
| 1 | Iowa City Water Department | 68,753 | 111 |
| 2 | University Water System | 26,684 | 84 |
| 3 | Lake Ridge, Incorporated | 1,300 | 84 |
| 4 | Modern Manor, Inc. | 915 | 84 |
| 5 | Iowa City Regency Mobile Home Community | 700 | 84 |
31 total water systems serve Johnson County.
All ZIP Codes in Johnson County
13 ZIP codes tracked in Johnson County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 52235 | Hills | 66 | C | 0 | $218K |
| 2 | 52317 | North Liberty | 66 | C | 3 | $315K |
| 3 | 52340 | Tiffin | 66 | C | 3 | $318K |
| 4 | 52338 | Swisher | 65 | C | 12 (2 health) | $385K |
| 5 | 52333 | Solon | 63 | C | 1 | $348K |
| 6 | 52322 | Oxford | 55 | C | 22 (2 health) | $249K |
| 7 | 52241 | Coralville | 52 | D | 5 | $286K |
| 8 | 52242 | Iowa City | 51 | D | 14 | — |
| 9 | 52245 | Iowa City | 51 | D | 14 | $293K |
| 10 | 52243 | Iowa City | 50 | D | 14 | — |
| 11 | 52244 | Iowa City | 50 | D | 14 | — |
| 12 | 52240 | Iowa City | 46 | D | 14 | $241K |
| 13 | 52246 | Iowa City | 46 | D | 14 | $327K |
Recommended Buyer Guides for Johnson County
While many sites publish identical guide lists across every county they cover, the selection here changes by location — driven by the EPA, NSF, FEMA, and CDC datasets that describe the actual conditions documented for this jurisdiction in the federal record.
- Best Under-Sink Reverse Osmosis Systems — Multi-contaminant removal at the kitchen tap
- Best Radon Test Kits — EPA Radon Zone 1 (highest risk) dominant in county
- 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 Johnson County, Iowa
Overview
Johnson County in Iowa covers 13 ZIP codes with an average Home Safety Score of C (56/100).
12 of 13 ZIP codes have recorded EPA violations. 4 health-based violations have been documented.
← Back to Iowa 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.