Custer County, Idaho
6 ZIP codes · Avg score 49/100 · Grade D · Updated 2026-06-03
Covering 6 ZIP codes, Custer County falls in the bottom tier for tap water safety — health-based violations are a recurring pattern, and the county's grade signals that residents should check system-level detail for their specific address.
How Custer County Compares
How Custer County Compares
Custer County scores 17 points below the Idaho state average (66/100) and 19 points below the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-03
ZIP Code Risk Map
Water Quality Map: Custer County, Idaho
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Key Risk Factors
Health risk index: 14.2 (asthma 10.5%, diabetes 13.3%)
Estimated additional annual cost per homeowner: $722, driven primarily by energy_code_gap
Infrastructure: 0.325% avg pipe failure probability
56.5% 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: $722
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Housing Age Distribution
3,147 housing units in Custer 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 Custer County
Remediation costs are relatively manageable for most homeowners in Custer 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 Custer County residents
Black markers = national averages. Red = above national avg. Green = below. Source: CDC PLACES, Census ACS.
Water Systems with Most Violations
Top 3 systems in Custer County ranked by EPA violation count.
| # | Water System | Population | Violations |
|---|---|---|---|
| 1 | City of Challis | 900 | 13 |
| 2 | Round Valley Water Assn | 125 | 13 |
| 3 | City of Mackay | 566 | 0 |
All ZIP Codes in Custer County
6 ZIP codes tracked in Custer County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 83251 | Mackay | 70 | B | 0 | $327K |
| 2 | 83253 | May | 53 | D | 0 | — |
| 3 | 83226 | Challis | 51 | D | 13 | $271K |
| 4 | 83227 | Clayton | 40 | D | 0 | — |
| 5 | 83235 | Ellis | 40 | D | 0 | — |
| 6 | 83278 | Stanley | 40 | D | 0 | $618K |
Recommended Buyer Guides for Custer County
Filtered against EPA monitoring data and CDC lead-exposure guidance, the guides below skip the generic catalog and connect directly to the contaminants and hazards on file here.
- Best Lead Paint Test Kits — 56.5% of homes built before 1978
- Best Radon Test Kits — EPA Radon Zone 1 (highest risk) dominant in county
Deep Dive Reports
Detailed analysis for Custer County, Idaho
Overview
Custer County in Idaho covers 6 ZIP codes with an average Home Safety Score of D (49/100).
1 of 6 ZIP codes have recorded EPA violations. All violations are monitoring/reporting type.
← Back to Idaho 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.
What You Can Do
Custer County has a grade of D. Here are steps to protect your household.
Test your tap water
Order a certified lab test kit ($20-$50) to check for lead, bacteria, and other contaminants specific to your ZIP code.
Consider a certified water filter
NSF-certified filters can remove most common contaminants. Match the filter to your test results for best protection. Try our filter matcher
Contact your water utility
Request the latest Consumer Confidence Report (CCR) from your water provider. It details exactly what was found in your water supply.
Check for lead in your home
56.5% of homes in this county were built before 1978. Older plumbing and solder can leach lead into drinking water, especially in the morning.