Septic tank size by state / West North Central
North Dakota septic tank size
In North Dakota the minimum septic tank for a three-bedroom house is 1,000 gallons, rising to 1,200 gallons at four bedrooms. The figure comes from N.D. Admin. Code 62-03.1-03-07(1) (Septic tanks). That matches the 1,000-gallon median of the 47 states listed here.
What the North Dakota rule says
The rule is N.D. Admin. Code 62-03.1-03-07(1) (Septic tanks), administered by North Dakota State Plumbing Board rules (N.D. Admin. Code Title 62), enforced by ND DEQ and local/district health units as administrative authority. In its own words:
Table "Single-Family Dwellings - Number of Bedrooms" / "Minimum Septic Tank Working Capacity in Gallons": 1-3 1,000; 4 1,200; 5 or 6 1,500; 7 or 8 2,000; "Extra bedroom, 150 gallons each." Sizes "include sludge storage capacity and the connection of domestic food waste disposal units without further volume increase."
Source: N.D. Admin. Code 62-03.1-03-07(1) (Septic tanks), read 2026-10-20.
- Five and six-bedroom homes share the 1,500-gallon row; there is no garbage-disposal increase.
- Several counties, such as Cass and Grand Forks, have their own ordinances.
North 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 | 1,200 gal | same |
| 5 | 1,500 gal | same |
| 6 | 1,500 gal | — |
The first step up comes at 4 bedrooms, from 1,000 to 1,200 gallons, and a six-bedroom house needs 1,500 gallons. Beyond the table the rule adds 150 gallons for each extra bedroom. These are minimums: the permit can call for more, and a bigger tank needs pumping less often.
How North 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; South Dakota requires 1,000 gallons for three bedrooms. 37 of the 47 states listed here share North Dakota's three-bedroom figure.
Before you size a tank in North 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 North 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.