Septic tank size by state / West North Central
Minnesota septic tank size
In Minnesota the minimum septic tank for a three-bedroom house is 1,000 gallons, rising to 1,500 gallons at four bedrooms. The figure comes from Minn. R. 7080.1930 (Septic tank capacity), Table V. That matches the 1,000-gallon median of the 47 states listed here.
What the Minnesota rule says
The rule is Minn. R. 7080.1930 (Septic tank capacity), Table V, administered by Minnesota Pollution Control Agency (counties/local units administer). In its own words:
Subp. 1: "The liquid capacity of septic tanks must be at least as large as the liquid capacities given in Table V." Table V: 3 or less 1,000; 4 or 5 1,500; 6 or 7 2,000; 8 or 9 2,500. Over nine: 2,500 + ([# of bedrooms - 9] x 250). Subp. 2: "If a garbage disposal unit is anticipated or installed in a dwelling, the septic tank capacity must be at least 50 percent greater than that required in subpart 1"
Source: Minn. R. 7080.1930 (Septic tank capacity), Table V, read 2026-10-20.
- A garbage disposal adds 50% and calls for multiple compartments or tanks.
- The tank steps up in pairs of bedrooms: 1,500 gallons for four or five, 2,000 for six or seven.
Minnesota 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 | 1,500 gal | +300 |
| 5 | 1,500 gal | same |
| 6 | 2,000 gal | — |
The first step up comes at 4 bedrooms, from 1,000 to 1,500 gallons, and a six-bedroom house needs 2,000 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 Minnesota compares with nearby states
Iowa requires 1,250 gallons for three bedrooms; Kansas 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; South Dakota requires 1,000 gallons for three bedrooms. 37 of the 47 states listed here share Minnesota's three-bedroom figure.
Before you size a tank in Minnesota
- 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 Minnesota'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.