South Dakota · Administrative Rules of South Dakota Article 74:53
South Dakota DANR administers the program, with licensing of installers and designers.
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 east of the Missouri River with heavy clay, and drier, sandier ground to the west. The Black Hills have shallow rock and steep slopes. Frost depth is severe statewide.
Conventional trenches where soil allows, mounds on tight eastern clay, and lagoons on rural acreages. Deep burial and insulation address frost.
| 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 |
South Dakota licenses installers and requires design in accordance with the state rules; local requirements are lighter than in many states, with more reliance on the state framework.
The state sets a floor. These South Dakota counties are where the largest septic populations sit, and where local requirements most often exceed it.
| County | What makes it different |
|---|---|
| Minnehaha | Sioux Falls area; till clay |
| Pennington | Rapid City and Black Hills; rock and slope |
| Lincoln | Fast growth south of Sioux Falls |
| Lawrence | Black Hills, difficult excavation |
| Brown | Aberdeen area, eastern clay |
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.
No statewide mandated interval; cold soil argues for shorter intervals. Use the pump schedule calculator to work out the interval for your tank size and household.
Regional labour and permit costs in South Dakota run about 94% of the national baseline. Here is what typical installations land at for a three-bedroom home:
| System type | Typical installed cost in South Dakota | When it applies |
|---|---|---|
| Conventional gravity | $8,500 – $15,000 | Good soil, adequate depth to water |
| Chamber system | $9,400 – $17,200 | Alternative to gravel trenches |
| Mound system | $16,200 – $31,500 | Shallow water table or thin soil |
| Aerobic treatment | $13,600 – $27,000 | Clay soil or small lots |
| Tank pump-out (service) | $300 – $610 | 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 Administrative Rules of South Dakota Article 74:53, On-Site Wastewater Systems. County and health district rules routinely exceed them, code text changes, and only South Dakota DANR — Wastewater Program or your local health department can confirm what applies to your parcel.
Send your sizing numbers to installers who work under South Dakota rules every day.