Septic Systems in Iowa

99 counties · ~18% of homes on septic · ~225,629 septic systems

State Regulation Overview

Regulatory Body
Iowa DNR
Inspection Required for Sale
Yes
Nitrogen Reduction Areas
No
Advanced Treatment Areas
No

Septic inspection required for deed transfer. Time of Transfer inspections mandatory.

Top Counties by Septic Systems

Polk County
~17,726 septic homes
Linn County
~12,436 septic homes
Scott County
~9,432 septic homes
Johnson County
~8,254 septic homes
Dallas County
~7,177 septic homes

All Counties in Iowa

Adair County
7K pop · ~25.2% septic
Adams County
4K pop · ~28.8% septic
Allamakee County
14K pop · ~25.2% septic
Appanoose County
12K pop · ~25.2% septic
Audubon County
6K pop · ~25.2% septic
Benton County
26K pop · ~21.6% septic
Black Hawk County
131K pop · ~13.5% septic
Boone County
27K pop · ~21.6% septic
Bremer County
25K pop · ~21.6% septic
Buchanan County
21K pop · ~21.6% septic
Buena Vista County
21K pop · ~21.6% septic
Butler County
14K pop · ~25.2% septic
Calhoun County
10K pop · ~25.2% septic
Carroll County
21K pop · ~21.6% septic
Cass County
13K pop · ~25.2% septic
Cedar County
19K pop · ~21.6% septic
Cerro Gordo County
43K pop · ~21.6% septic
Cherokee County
12K pop · ~25.2% septic
Chickasaw County
12K pop · ~25.2% septic
Clarke County
10K pop · ~25.2% septic
Clay County
16K pop · ~21.6% septic
Clayton County
17K pop · ~21.6% septic
Clinton County
46K pop · ~21.6% septic
Crawford County
17K pop · ~21.6% septic
Dallas County
100K pop · ~18% septic
Davis County
9K pop · ~25.2% septic
Decatur County
8K pop · ~25.2% septic
Delaware County
17K pop · ~21.6% septic
Des Moines County
39K pop · ~21.6% septic
Dickinson County
18K pop · ~21.6% septic
Dubuque County
99K pop · ~18% septic
Emmet County
9K pop · ~25.2% septic
Fayette County
20K pop · ~21.6% septic
Floyd County
16K pop · ~21.6% septic
Franklin County
10K pop · ~25.2% septic
Fremont County
7K pop · ~25.2% septic
Greene County
9K pop · ~25.2% septic
Grundy County
12K pop · ~25.2% septic
Guthrie County
11K pop · ~25.2% septic
Hamilton County
15K pop · ~21.6% septic
Hancock County
11K pop · ~25.2% septic
Hardin County
17K pop · ~21.6% septic
Harrison County
15K pop · ~25.2% septic
Henry County
20K pop · ~21.6% septic
Howard County
9K pop · ~25.2% septic
Humboldt County
10K pop · ~25.2% septic
Ida County
7K pop · ~25.2% septic
Iowa County
17K pop · ~21.6% septic
Jackson County
19K pop · ~21.6% septic
Jasper County
38K pop · ~21.6% septic
Jefferson County
16K pop · ~21.6% septic
Johnson County
153K pop · ~13.5% septic
Jones County
21K pop · ~21.6% septic
Keokuk County
10K pop · ~25.2% septic
Kossuth County
15K pop · ~25.2% septic
Lee County
34K pop · ~21.6% septic
Linn County
230K pop · ~13.5% septic
Louisa County
11K pop · ~25.2% septic
Lucas County
9K pop · ~25.2% septic
Lyon County
12K pop · ~25.2% septic
Madison County
17K pop · ~21.6% septic
Mahaska County
22K pop · ~21.6% septic
Marion County
33K pop · ~21.6% septic
Marshall County
40K pop · ~21.6% septic
Mills County
14K pop · ~25.2% septic
Mitchell County
11K pop · ~25.2% septic
Monona County
9K pop · ~25.2% septic
Monroe County
8K pop · ~25.2% septic
Montgomery County
10K pop · ~25.2% septic
Muscatine County
43K pop · ~21.6% septic
O'Brien County
14K pop · ~25.2% septic
Osceola County
6K pop · ~25.2% septic
Page County
15K pop · ~21.6% septic
Palo Alto County
9K pop · ~25.2% septic
Plymouth County
26K pop · ~21.6% septic
Pocahontas County
7K pop · ~25.2% septic
Polk County
492K pop · ~9% septic
Pottawattamie County
94K pop · ~18% septic
Poweshiek County
19K pop · ~21.6% septic
Ringgold County
5K pop · ~28.8% septic
Sac County
10K pop · ~25.2% septic
Scott County
175K pop · ~13.5% septic
Shelby County
12K pop · ~25.2% septic
Sioux County
36K pop · ~21.6% septic
Story County
99K pop · ~18% septic
Tama County
17K pop · ~21.6% septic
Taylor County
6K pop · ~25.2% septic
Union County
12K pop · ~25.2% septic
Van Buren County
7K pop · ~25.2% septic
Wapello County
35K pop · ~21.6% septic
Warren County
52K pop · ~18% septic
Washington County
23K pop · ~21.6% septic
Wayne County
6K pop · ~25.2% septic
Webster County
37K pop · ~21.6% septic
Winnebago County
11K pop · ~25.2% septic
Winneshiek County
20K pop · ~21.6% septic
Woodbury County
106K pop · ~13.5% septic
Worth County
7K pop · ~25.2% septic
Wright County
13K pop · ~25.2% septic

Septic Systems in Iowa

Approximately 18% of homes in Iowa rely on septic systems for wastewater treatment, totaling an estimated 225,629 septic systems across the state's 99 counties. This places Iowa among the states with significant decentralized wastewater infrastructure.

Septic Regulations in Iowa

Septic regulations in Iowa are administered by Iowa DNR, with permits typically issued at the county level through local health departments. Requirements for tank sizes, setback distances, approved system types, and inspections can vary significantly between counties.

Iowa requires septic system inspections as part of real estate transactions. Sellers must demonstrate that their septic system is functioning properly before a property sale can close. This typically involves hiring a licensed inspector to evaluate the tank, distribution box, and drainfield.

Common Septic System Types

Homeowners in Iowa typically use one of several septic system types depending on local soil conditions: conventional gravity-fed systems where soil percolation is adequate, pressure distribution systems in areas with moderate limitations, mound systems where shallow bedrock or high water tables prevent conventional installation, and aerobic treatment units (ATUs) in environmentally sensitive areas.

Septic Maintenance Requirements

The EPA recommends pumping septic tanks every 3 to 5 years, though the exact frequency depends on tank size, household size, and water usage. In Iowa, some counties have adopted mandatory pumping schedules or maintenance tracking programs. Proper maintenance prevents costly repairs, protects groundwater quality, and extends the lifespan of the drainfield — the most expensive component to replace.

Select a county above to view detailed septic regulations, estimated costs, soil suitability data sourced from the USDA NRCS Soil Survey, and groundwater depth measurements from the USGS.

Data last updated: 2026-04-13