Sully County, South Dakota
3 ZIP codes · Avg score 52/100 · Grade D · Updated 2026-06-03
Sully County ranks below average for water safety, with health-based violations recorded across multiple of its 3 ZIP codes.
How Sully County Compares
How Sully County Compares
Sully County scores 8 points below the South Dakota state average (60/100) and 16 points below the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-03
Key Risk Factors
Health risk index: 13.2 (asthma 9.8%, diabetes 11.9%)
Estimated additional annual cost per homeowner: $1,077, driven primarily by flood
Infrastructure: 0.407% avg pipe failure probability, 33% of ZIPs at high risk
73% 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: $1,077
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Housing Age Distribution
865 housing units in Sully 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 Sully County
Remediation costs are relatively manageable for most homeowners in Sully 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 Sully County residents
Black markers = national averages. Red = above national avg. Green = below. Source: CDC PLACES, Census ACS.
All ZIP Codes in Sully County
3 ZIP codes tracked in Sully County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 57564 | Onida | 70 | B | 0 | $199K |
| 2 | 57522 | Blunt | 45 | D | 0 | $179K |
| 3 | 57520 | Agar | 40 | D | 0 | $114K |
Recommended Buyer Guides for Sully County
Editorial methodology pairs each documented risk in this county with the buyer category that addresses it, drawing on water-quality detections, housing-stock lead exposure, EPA Radon Zone designation, and FEMA flood and wildfire ratings. NSF-certified options surface where applicable, and products that match the specific contaminant take priority.
- Best Lead Paint Test Kits — 73% of homes built before 1978
- 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
Overview
Sully County in South Dakota covers 3 ZIP codes with an average Home Safety Score of D (52/100).
No EPA violations recorded across any tracked ZIP codes in Sully County.
← Back to South Dakota 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
Sully 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
73% of homes in this county were built before 1978. Older plumbing and solder can leach lead into drinking water, especially in the morning.