Monroe County, Wisconsin
12 ZIP codes · Avg score 69/100 · Grade C · Updated 2026-06-03
Tracking 12 ZIP codes in Monroe County reveals a mixed picture — tap water quality varies meaningfully by location.
How Monroe County Compares
How Monroe County Compares
Monroe County scores 3 points above the Wisconsin state average (66/100) and 1 points above the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-03
ZIP Code Risk Map
Water Quality Map: Monroe County, Wisconsin
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Key Risk Factors
Health risk index: 14.7 (asthma 11.2%, diabetes 13%)
Estimated additional annual cost per homeowner: $793, driven primarily by flood
Infrastructure: 0.371% avg pipe failure probability, 22% of ZIPs at high risk
62.3% of homes built before 1978 (lead paint era)
Violation History (2022–2025)
↑ Worsening trendEPA violation counts by year across Monroe County water systems. Health-based shown in red, total in blue.
Peak year: 2024 with 3 violations. Past 5 years: 9 total (9 health-based). Health-based violations are rising versus the prior 2-year window — worth closer monitoring.
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: $793
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Housing Age Distribution
19,741 housing units in Monroe 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 Monroe County
Remediation costs are relatively manageable for most homeowners in Monroe 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 Monroe 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 Monroe County ranked by EPA violation count.
| # | Water System | Population | Violations |
|---|---|---|---|
| 1 | Kendall Waterworks | 458 | 11 |
| 2 | SPARTA WATERWORKS | 10,025 | 6 |
| 3 | Cortland Acres | 145 | 6 |
| 4 | Oakdale Waterworks | 317 | 2 |
| 5 | Pleasant Prairie Mhp | 35 | 2 |
11 total water systems serve Monroe County.
All ZIP Codes in Monroe County
12 ZIP codes tracked in Monroe County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 54648 | Norwalk | 83 | B | 0 | $173K |
| 2 | 54649 | Oakdale | 82 | B | 2 (1 health) | — |
| 3 | 54619 | Cashton | 78 | B | 0 | $217K |
| 4 | 54666 | Warrens | 75 | B | 0 | $193K |
| 5 | 54656 | Sparta | 74 | B | 6 | $201K |
| 6 | 54660 | Tomah | 74 | B | 1 (1 health) | $188K |
| 7 | 54670 | Wilton | 73 | B | 2 (2 health) | $217K |
| 8 | 54638 | Kendall | 72 | B | 11 (3 health) | $259K |
| 9 | 54620 | Cataract | 53 | D | 0 | — |
| 10 | 54641 | Mather | 53 | D | 0 | — |
| 11 | 54643 | Millston | 53 | D | 0 | — |
| 12 | 54662 | Tunnel City | 53 | D | 0 | — |
Recommended Buyer Guides for Monroe 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 Lead Paint Test Kits — 62.3% 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 Monroe County, Wisconsin
Overview
Monroe County in Wisconsin covers 12 ZIP codes with an average Home Safety Score of C (69/100).
5 of 12 ZIP codes have recorded EPA violations. 7 health-based violations have been documented.
← Back to Wisconsin 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.