South Dakota · S.D. Admin. R. 74:53:01:25
Septic system requirements in South Dakota
Tank sizes, drainfield rules, setbacks, permits, and real costs — pulled from South Dakota's own code rather than a national average.
- 3-bedroom tank
- 1,000 gal
- Design flow
- 150 gpd/BR
- Typical install
- $7,000–$19,000
- Permit fee
- $100–$400
- Well setback
- 100 ft
- Permitted by
- County / local
Septic tank sizes required in South Dakota
South Dakota sizes systems on a design flow of 150 gallons per day per bedroom, with every dwelling rated for at least 3 bedrooms. The tank must meet both the bedroom table below and a 2× daily-flow detention requirement — whichever produces the larger number governs.
| Bedrooms | Design flow | Code minimum | Recommended |
|---|---|---|---|
| 1 bedroom | 450 gpd | 1,000 gal | 1,000 gal |
| 2 bedrooms | 450 gpd | 1,000 gal | 1,000 gal |
| 3 bedrooms | 450 gpd | 1,000 gal | 1,000 gal |
| 4 bedrooms | 600 gpd | 1,000 gal | 1,250 gal |
| 5 bedrooms | 750 gpd | 1,250 gal | 1,500 gal |
| 6 bedrooms | 900 gpd | 1,500 gal | 2,000 gal |
Source: S.D. Admin. R. 74:53:01:25. The recommended column rounds the governing requirement up to a tank size manufacturers actually stock.Run your own numbers →
Drainfield size and cost by soil type
For a three-bedroom home in South Dakota at 450 gpd. This single table explains most of the variation between quotes — the area scales inversely with how fast your soil accepts water, and the drainfield is the largest line item in the job.
| Soil | Loading rate | Absorption area | With reserve | Typical total install |
|---|---|---|---|---|
| Medium sand | 0.8 gpd/ft² | 563 ft² | 1,126 ft² | $9,800 |
| Sandy loam | 0.5 gpd/ft² | 900 ft² | 1,800 ft² | $12,500 |
| Loam | 0.4 gpd/ft² | 1,125 ft² | 2,250 ft² | $14,300 |
| Silt loam | 0.3 gpd/ft² | 1,500 ft² | 3,000 ft² | $17,300 |
| Clay loam | 0.2 gpd/ft² | 2,250 ft² | 4,500 ft² | $23,200 |
Estimates use South Dakota's cost index of 0.88× the national average. Build a line-item estimate →
Permits and who issues them
Counties permit systems under state administrative rules; DANR reviews larger systems and subdivisions.
| Permit required | Yes |
|---|---|
| Typical fee | $100 – $400 |
| Soil evaluation | Required before permit |
| Licensed installer | Not required statewide |
| Turnaround | 1–4 weeks |
| Ongoing inspection | Not mandated statewide |
| Reserve area | 100% replacement area required |
Minimum setback distances
Measured horizontally from the drainfield unless noted. Local rules are frequently stricter, and on a small lot these numbers — not the soil — often decide the layout.
| Private water well | 100 ft |
|---|---|
| Well (septic tank) | 50 ft |
| Property line | 10 ft |
| Surface water | 50 ft |
| Building foundation | 10 ft |
Regulatory contact
South Dakota DANR — Surface Water Quality
danr.sd.gov · 605-773-3351
What makes septic hard in South Dakota
Deep frost and a short season constrain when work can happen.
East River glacial till is dense and slowly permeable; West River gumbo clay is worse.
Black Hills sites hit rock quickly and have steep slopes.
Things that catch people out
- Every dwelling is designed for at least three bedrooms regardless of actual size, so a small cabin still needs a full-size system.
- The design flow is the greater of 150 gpd per bedroom or 3.5 persons at 90 gpd each.
South Dakota septic questions
What size septic tank do I need in South Dakota?
A three-bedroom home in South Dakota requires a minimum 1,000 gallon tank under S.D. Admin. R. 74:53:01:25. Design flow is 150 gallons per day per bedroom, and the tank must also hold 2 times daily flow, so the practical recommendation is 1,000 gallons.
Do I need a permit for a septic system in South Dakota?
Yes. Counties permit systems under state administrative rules; DANR reviews larger systems and subdivisions. Fees typically run $100 to $400, with a turnaround of about 1–4 weeks. A soil evaluation or percolation test is required before a permit is issued.
How much does a septic system cost in South Dakota?
A conventional system for a three-bedroom home typically runs $7,000 to $19,000 installed. Soil quality moves this more than anything else — on tight clay requiring a mound, budget two to three times the low end.
How far must a South Dakota drainfield be from a well?
100 feet from a private water well, with the septic tank itself allowed at 50 feet. Local rules can be stricter.
Sources
Every figure on this page traces to one of these documents.
- S.D. Admin. R. 74:53:01:25 — Minimum capacities for septic tanks · verified 2026-09-18