Will my county's soil pass a septic perc test?
USDA's own soil survey already rates how well the ground percolates for a septic absorption field, county by county, for all 3,144 US counties. This shows you that rating, free, before you pay for a site-specific perc test.
The three answers this data can give
USDA rates every county's dominant soil into one of three classes for a standard septic absorption field:
- Very limited — 2,913 counties on this site. A conventional gravity system routinely fails here; budget for an engineered alternative.
- Somewhat limited — 145 counties. A conventional system can sometimes still work with design changes, but it isn't guaranteed.
- Not limited — no county on this site currently gets this reading as its dominant class - USDA's absorption-field criteria are strict nationwide. Where it does apply, a conventional system is the expected default.
What the difference costs
Sutton County, TX carries this site's most-constrained soil rating - see its page for what that looks like in practice.
Read this before you rely on it
This is a county-level figure. USDA's soil survey scores the dominant condition across a whole county's surveyed land, not one address. A real building permit still requires a site-specific percolation test - this exists to set expectations before you pay for one, not to replace it.
Browse all 3,144 counties by state
- Alabama67
- Alaska30
- Arizona15
- Arkansas75
- California58
- Colorado64
- Connecticut9
- Delaware3
- District of Columbia1
- Florida67
- Georgia159
- Hawaii5
- Idaho44
- Illinois102
- Indiana92
- Iowa99
- Kansas105
- Kentucky120
- Louisiana64
- Maine16
- Maryland24
- Massachusetts14
- Michigan83
- Minnesota87
- Mississippi82
- Missouri115
- Montana56
- Nebraska93
- Nevada17
- New Hampshire10
- New Jersey21
- New Mexico33
- New York62
- North Carolina100
- North Dakota53
- Ohio88
- Oklahoma77
- Oregon36
- Pennsylvania67
- Rhode Island5
- South Carolina46
- South Dakota66
- Tennessee95
- Texas254
- Utah29
- Vermont14
- Virginia133
- Washington39
- West Virginia55
- Wisconsin72
- Wyoming23
The question this site answers
Before spending $1,300 on a site-specific percolation test, most people want a rough sense of what to expect. USDA already scores it: its Soil Survey Geographic (SSURGO) database rates every county's dominant soil for a standard septic absorption field, free, for all 3,144 US counties. PercCheck reports that county-level rating straight from USDA's Soil Data Access, no guessing.
A county figure, not a permit
This is the county-wide, area-weighted dominant condition - useful for budgeting before you buy land or commit to a design, not a substitute for the site-specific perc test a health department will require before issuing a permit. One lot can differ from its county's average; this tells you what to expect walking in.