Minnesota · Minnesota Rules Chapters 7080 through 7083
The Minnesota Pollution Control Agency writes the SSTS rules and counties administer permitting through licensed professionals.
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 soils ranging from sandy outwash to heavy clay till, with a high water table in many areas and frost depth that reaches four to six feet. Karst in the southeast around the Root River adds groundwater vulnerability.
Minnesota's rules are among the most developed in the country. Type I conventional trenches, mounds, and at-grade systems are all standard, and mound systems are extremely common because of shallow water table and restrictive layers.
| 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 |
Minnesota licenses SSTS professionals in distinct classes — designer, installer, inspector, maintainer, service provider. A design must be produced by a licensed designer, and the county reviews it. Compliance inspections are required at property transfer in many counties.
The state sets a floor. These Minnesota counties are where the largest septic populations sit, and where local requirements most often exceed it.
| County | What makes it different |
|---|---|
| Anoka | Sandy soils, large septic population north of the Twin Cities |
| Washington | Suburban growth with strict county requirements |
| Crow Wing | Lake country; shoreline setbacks dominate |
| Otter Tail | Very high lake density, strict shoreland rules |
| Olmsted | Rochester; karst limestone in the southeast |
| Sherburne | Growth corridor on mixed soils |
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.
Minnesota requires that systems be maintained and many counties require a compliance inspection at transfer or with any permit activity. Use the pump schedule calculator to work out the interval for your tank size and household.
Regional labour and permit costs in Minnesota run about 105% of the national baseline. Here is what typical installations land at for a three-bedroom home:
| System type | Typical installed cost in Minnesota | When it applies |
|---|---|---|
| Conventional gravity | $9,400 – $16,800 | Good soil, adequate depth to water |
| Chamber system | $10,300 – $19,300 | Alternative to gravel trenches |
| Mound system | $17,900 – $35,300 | Shallow water table or thin soil |
| Aerobic treatment | $15,000 – $30,200 | Clay soil or small lots |
| Tank pump-out (service) | $340 – $680 | 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 Minnesota Rules Chapters 7080 through 7083, Subsurface Sewage Treatment Systems. County and health district rules routinely exceed them, code text changes, and only Minnesota PCA — Subsurface Sewage Treatment Systems or your local health department can confirm what applies to your parcel.
Send your sizing numbers to installers who work under Minnesota rules every day.