Knox County, Maine
18 ZIP codes · Avg score 70/100 · Grade B · Updated 2026-06-03
Knox County's tap water quality puts it in the upper tier nationally; the 18 ZIP codes here record few health-based violations.
How Knox County Compares
How Knox County Compares
Knox County scores 13 points above the Maine state average (57/100) and 2 points above the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-03
ZIP Code Risk Map
Water Quality Map: Knox County, Maine
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Key Risk Factors
Health risk index: 13.3 (asthma 11.9%, diabetes 11.2%)
Estimated additional annual cost per homeowner: $1,137, driven primarily by energy_code_gap
Infrastructure: 0.421% avg pipe failure probability, 67% of ZIPs at high risk
66.6% of homes built before 1978 (lead paint era)
Violation History (2021–2025)
↑ Worsening trendEPA violation counts by year across Knox County water systems. Health-based shown in red, total in blue.
Peak year: 2024 with 13 violations. Past 5 years: 27 total (27 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: $1,137
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Housing Age Distribution
23,497 housing units in Knox 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 Knox County
Remediation costs are relatively manageable for most homeowners in Knox 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 Knox 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 Knox County ranked by EPA violation count.
| # | Water System | Population | Violations |
|---|---|---|---|
| 1 | Maine Water Company Camden & Rockland | 21,315 | 23 |
| 2 | Village at Rockport #4 | 43 | 20 |
| 3 | Village at Rockport #1 | 30 | 20 |
| 4 | Mountainside Mobile Home Park | 130 | 16 |
| 5 | Ducktrap Harbor Condominiums | 83 | 13 |
19 total water systems serve Knox County.
All ZIP Codes in Knox County
18 ZIP codes tracked in Knox County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 4547 | Friendship | 83 | B | 1 | $265K |
| 2 | 4853 | North Haven | 83 | B | 1 | $405K |
| 3 | 4858 | South Thomaston | 83 | B | 0 | $305K |
| 4 | 4864 | Warren | 83 | B | 0 | $216K |
| 5 | 4855 | Port Clyde | 82 | B | 3 | $359K |
| 6 | 4861 | Thomaston | 82 | B | 3 (1 health) | $260K |
| 7 | 4862 | Union | 82 | B | 3 (1 health) | $237K |
| 8 | 4856 | Rockport | 75 | B | 7 (5 health) | $415K |
| 9 | 4854 | Owls Head | 71 | B | 6 | $332K |
| 10 | 4843 | Camden | 69 | C | 13 (6 health) | $486K |
| 11 | 4841 | Rockland | 63 | C | 0 | $234K |
| 12 | 4852 | Monhegan | 63 | C | 0 | $688K |
| 13 | 4859 | Spruce Head | 63 | C | 0 | $744K |
| 14 | 4860 | Tenants Harbor | 63 | C | 0 | $310K |
| 15 | 4863 | Vinalhaven | 58 | C | 9 (7 health) | $436K |
| 16 | 4563 | Cushing | 53 | D | 0 | $371K |
| 17 | 4574 | Washington | 53 | D | 0 | $187K |
| 18 | 4851 | Matinicus | 53 | D | 0 | $425K |
Recommended Buyer Guides for Knox County
Where county records show a lead exceedance or pre-1978 housing concentration, lead-specific filters and test kits move toward the top of the list.
- Best Lead Paint Test Kits — 66.6% of homes built before 1978
- Best Under-Sink Reverse Osmosis Systems — Multi-contaminant removal at the kitchen tap
Deep Dive Reports
Detailed analysis for Knox County, Maine
Overview
Knox County in Maine covers 18 ZIP codes with an average Home Safety Score of B (70/100).
9 of 18 ZIP codes have recorded EPA violations. 20 health-based violations have been documented.
← Back to Maine 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.