Indiana · 410 IAC 6-8.3
The Indiana Department of Health writes the rule and local health departments issue permits, with authority to be more restrictive.
Minimum tank
One to three bedroom dwelling.
Design flow
Held two days for settling.
Cost index
Regional labour and permits.
Sets the design flow and the legal minimum.
Code sizes on bedrooms, not people.
Used to size the matching drainfield. Unsure? Sandy loam is the common default.
Glacial till across most of the state with slow-percolating silty clay loam. Northern Indiana has sandy outwash areas that permit easily. Southern Indiana has karst limestone and thin soils over rock.
Indiana's rule is built around soil loading rates from a soil morphology evaluation rather than perc tests, and it makes heavy use of pressure distribution. Elevated sand mounds are common on tight soils.
| Dwelling | Design flow | Minimum tank | With disposal |
|---|---|---|---|
| 1 bedroom | 300 gpd | 1,000 gal | 1,250 gal |
| 2 bedrooms | 300 gpd | 1,000 gal | 1,250 gal |
| 3 bedrooms | 450 gpd | 1,000 gal | 1,250 gal |
| 4 bedrooms | 600 gpd | 1,250 gal | 1,500 gal |
| 5 bedrooms | 750 gpd | 1,500 gal | 1,750 gal |
Indiana requires a soil evaluation by a registered soil scientist, and the rule specifies loading rates by soil texture and structure. Perc tests alone are not the basis of design.
The state sets a floor. These Indiana counties are where the largest septic populations sit, and where local requirements most often exceed it.
| County | What makes it different |
|---|---|
| Hamilton | Fast suburban growth north of Indianapolis |
| Hendricks | Suburban expansion on till soils |
| Porter | Northwest Indiana, mixed sand and till |
| Monroe | Bloomington; karst limestone constraints |
| Kosciusko | Lake country with strict shoreline setbacks |
A three-bedroom home at 150 gallons per bedroom produces 450 gallons per day of design flow. On sandy loam that needs roughly 750 square feet of absorption area. On clay loam it rises to about 2,250 square feet, and on clay a conventional field is usually not permitted at all. Run your own soil class through the drainfield calculator.
Local health departments may impose maintenance requirements on advanced systems. Use the pump schedule calculator to work out the interval for your tank size and household.
Regional labour and permit costs in Indiana run about 96% of the national baseline. Here is what typical installations land at for a three-bedroom home:
| System type | Typical installed cost in Indiana | When it applies |
|---|---|---|
| Conventional gravity | $8,600 – $15,400 | Good soil, adequate depth to water |
| Chamber system | $9,500 – $17,700 | Alternative to gravel trenches |
| Mound system | $16,300 – $32,300 | Shallow water table or thin soil |
| Aerobic treatment | $13,800 – $27,700 | Clay soil or small lots |
| Tank pump-out (service) | $310 – $620 | Every 3–5 years |
Replacing an existing system costs more than these figures — old-system removal and re-permitting add to every line. The replacement cost calculator covers that case, and the cost estimator adjusts all of the above for your bedroom count and soil.
Verify before you build. The figures above are state minimums compiled for planning, drawn from 410 IAC 6-8.3, Residential Onsite Sewage Systems. County and health district rules routinely exceed them, code text changes, and only Indiana DOH — Residential Onsite Sewage Systems or your local health department can confirm what applies to your parcel.
Send your sizing numbers to installers who work under Indiana rules every day.