Septic system requirements in Illinois
What landplan.io applies when it designs a septic system in Illinois: the system types allowed, tank sizes, setbacks and soil loading rates, with what septic products cost there.
Updated
Design a septic system for an address in Illinois
Reviewed landplan.io designs by Illinois's own rules, which our staff reviewed against the state's regulations. Last published 5 October 2026.
Septic systems allowed in Illinois
The system types landplan.io permits in Illinois:
- Subsurface seepage bed
- Subsurface seepage field
- Drip Irrigation System
- Low Pressure Distribution
- Infiltrator Advanced Treatment Leachfield (ATL)
- Infiltrator Advanced Enviro-Septic® (AES)
- Surface Discharging System
Septic tank size in Illinois
The daily design flow of a home: 150 gal/day per bedroom, at least 240 gal/day. The septic tank is sized from that flow:
| Daily design flow | Minimum tank |
|---|---|
| up to 240 gal/day | 1,000 gallons |
| 240 to 360 gal/day | 1,500 gallons |
| 360 to 600 gal/day | 2,000 gallons |
| 600 to 720 gal/day | 2,500 gallons |
| 720 to 840 gal/day | 2,750 gallons |
| 840 to 920 gal/day | 3,000 gallons |
| 920 to 1,040 gal/day | 3,250 gallons |
Septic setbacks in Illinois
| From | To | Distance |
|---|---|---|
| Polygon | Existing Septic Component to be Abandoned | 5 ft |
These are the values the landplan.io design engine applies in Illinois. Confirm a design with the Illinois health department or your county's before you build.
Septic system costs in Illinois
| Product | Median | Typical range | Listings |
|---|---|---|---|
| Septic Tank | $1,957 | $1,700 – $2,100 | 14 |
The Illinois price index: every product type, month by month.
Parcel data in Illinois
landplan.io has parcel boundaries for 78 of Illinois's 102 counties, and part of 2 more: the counties where 94.9% of the state's people live. Type an address there and the design starts from the parcel.
Septic companies, designers and jobs in Illinois
- Septic companies and distributors in Illinois (84)
- Septic designers in Illinois
- Septic design jobs in Illinois
Where the rules come from
The regulations and documents landplan.io's Illinois rules are read from:
- Private Sewage Disposal Code (77 Ill. Admin. Code Part 905)
- Illinois Water Well Construction Code: Section 920.180 Closed Loop Wells and Table C Minimal Lateral Distances (77 Ill. Adm. Code 920.180; 77 Ill. Adm. Code 920.Table C)
- Part 905 Private Sewage Disposal Code, Appendix A: Illustrations and Exhibits (Illustrations A, C-X) (77 Ill. Adm. Code 905.Appendix A, Illustrations A-X)
- Section 905.Illustration D - Location of Components of Private Sewage Disposal Systems (minimum distances) (77 Ill. Adm. Code 905.Appendix A, Illustration D)
Septic rules by county in Illinois
- Adams County
- Alexander County
- Bond County
- Boone County
- Brown County
- Bureau County
- Calhoun County
- Carroll County
- Cass County
- Champaign County
- Christian County
- Clark County
- Clay County
- Clinton County
- Coles County
- Cook County
- Crawford County
- Cumberland County
- De witt County
- Dekalb County
- Douglas County
- DuPage County
- Edgar County
- Edwards County
- Effingham County
- Fayette County
- Ford County
- Franklin County
- Fulton County
- Gallatin County
- Greene County
- Grundy County
- Hamilton County
- Hancock County
- Hardin County
- Henderson County
- Henry County
- Iroquois County
- Jackson County
- Jasper County
- Jefferson County
- Jersey County
- Jo daviess County
- Johnson County
- Kane County
- Kankakee County
- Kendall County
- Knox County
- Lake County
- LaSalle County
- Lawrence County
- Lee County
- Livingston County
- Logan County
- Macon County
- Macoupin County
- Madison County
- Marion County
- Marshall County
- Mason County
- Massac County
- Mcdonough County
- McHenry County
- McLean County
- Menard County
- Mercer County
- Monroe County
- Montgomery County
- Morgan County
- Moultrie County
- Ogle County
- Peoria County
- Perry County
- Piatt County
- Pike County
- Pope County
- Pulaski County
- Putnam County
- Randolph County
- Richland County
- Rock island County
- Saline County
- Sangamon County
- Schuyler County
- Scott County
- Shelby County
- St clair County
- Stark County
- Stephenson County
- Tazewell County
- Union County
- Vermilion County
- Wabash County
- Warren County
- Washington County
- Wayne County
- White County
- Whiteside County
- Will County
- Williamson County
- Winnebago County
- Woodford County
Questions
What septic systems are allowed in Illinois?
landplan.io permits these system types in Illinois: Subsurface seepage bed, Subsurface seepage field, Drip Irrigation System, Low Pressure Distribution, Infiltrator Advanced Treatment Leachfield (ATL), Infiltrator Advanced Enviro-Septic® (AES) and Surface Discharging System.
What size septic tank do I need in Illinois?
landplan.io sizes the septic tank in Illinois from the daily design flow: up to 240 gal/day: 1,000 gallons; 240 to 360 gal/day: 1,500 gallons; 360 to 600 gal/day: 2,000 gallons; larger flows need larger tanks. A home's design flow is 150 gal/day per bedroom, at least 240 gal/day.
Does landplan.io have parcel data in Illinois?
Yes, for 78 of Illinois's 102 counties, and part of 2 more.