Septic tank size by state / West North Central
South Dakota septic tank size
In South Dakota the minimum septic tank for a three-bedroom house is 1,000 gallons, rising to 1,250 gallons at four bedrooms. The figure comes from ARSD 74:53:01:25(1). That matches the 1,000-gallon median of the 47 states listed here.
What the South Dakota rule says
The rule is ARSD 74:53:01:25(1), administered by South Dakota Department of Agriculture and Natural Resources (DANR). In its own words:
74:53:01:25. Minimum capacities for septic tanks. ... shall have a minimum capacity of at least 1,000 gallons of liquid ... each bedroom in excess of three shall require an additional 250-gallon increase ... If a septic tank receives wastes from a garbage disposal ... the overall capacity of the tank shall be increased by an additional 20 percent.
Source: ARSD 74:53:01:25(1), read 2026-10-20.
- A garbage disposal adds 20% to the tank.
- The rule covers homes with design flows of 750 gallons a day or less.
South Dakota minimum tank size by bedrooms
| Bedrooms | Minimum tank | Versus the median state |
|---|---|---|
| 1 | 1,000 gal | same |
| 2 | 1,000 gal | — |
| 3 | 1,000 gal | same |
| 4 | 1,250 gal | +50 |
| 5 | 1,500 gal | same |
| 6 | 1,750 gal | — |
The first step up comes at 4 bedrooms, from 1,000 to 1,250 gallons, and a six-bedroom house needs 1,750 gallons. Beyond the table the rule adds 250 gallons for each extra bedroom. These are minimums: the permit can call for more, and a bigger tank needs pumping less often.
How South Dakota compares with nearby states
Iowa requires 1,250 gallons for three bedrooms; Kansas requires 1,000 gallons for three bedrooms; Minnesota requires 1,000 gallons for three bedrooms; Missouri requires 1,000 gallons for three bedrooms; Nebraska requires 1,000 gallons for three bedrooms; North Dakota requires 1,000 gallons for three bedrooms. 37 of the 47 states listed here share South Dakota's three-bedroom figure.
Before you size a tank in South Dakota
- Bedrooms, not people, set the size in most rules. Rooms that could be used as bedrooms are usually counted, so check how your permitting office counts a den or a finished basement.
- Garbage disposals, grinder or ejector pumps and large tubs change the answer in many states; the points above list South Dakota's adjustments.
- The tank is only half the system. The drainfield is sized separately from soil tests, and it is usually the bigger cost.
- A private well on the same lot has its own setbacks from the tank and field; the well pump and pressure tank calculators size the water side.
Figures are the state's minimum as written on 2026-10-20. Local health departments can require more; the permit issued for your property governs. See the methodology for how each state was read.