State Requirements
Illinois Septic Tank Requirements
Complete guide to septic system requirements in Illinois (IL). Use our calculator for personalized recommendations.
Regulatory Agency
Illinois Department of Public Health
Permit Required
YesProfessional Install
RequiredMinimum Tank Size
1,000 gal
Tank Size Requirements
| Bedrooms | Min Tank Size | With Garbage Disposal |
|---|---|---|
| 3 | 1,000 gal | 1,500 gal |
| 4 | 1,250 gal | 1,875 gal |
| 1-2 | 1,000 gal | 1,500 gal |
| 5-6 | 1,500 gal | 2,250 gal |
Drainfield Sizing by Soil Type
Minimum square feet of absorption area based on soil percolation rate:
Gravel/Sandy
100
sq ft minimum
Sandy
150
sq ft minimum
Loam
200
sq ft minimum
Clay
300
sq ft minimum
Illinois Specific Notes
- Heavy clay soils common in central Illinois
- Floodplain restrictions apply
Regulatory Contact
Illinois Department of Public Health
Important Disclaimer
This information is provided for reference only. Local county or city requirements may be stricter than state minimums. Always verify requirements with your local health department before installation.
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