Septic tank size by state / West North Central
Kansas septic tank size
In Kansas 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 K.A.R. 28-5-6 to 28-5-9 and KDHE Bulletin 4-2, 'Minimum Standards for Design and Construction of Onsite Wastewater Systems' (March 1997), Table 7. That matches the 1,000-gallon median of the 47 states listed here.
What the Kansas rule says
The rule is K.A.R. 28-5-6 to 28-5-9 and KDHE Bulletin 4-2, 'Minimum Standards for Design and Construction of Onsite Wastewater Systems' (March 1997), Table 7, administered by Kansas Department of Health and Environment (KDHE); county sanitary codes. In its own words:
The minimum septic tank capacity is two times the daily wastewater flow ... Table 7: 1-3 bedrooms 1,000; 4: 1,200; 5: 1,500. Footnote: For each additional bedroom, add 300 gallons to the minimum value and 450 gallons to the recommended value. Minimum tank size is 1,000 gallons.
Source: K.A.R. 28-5-6 to 28-5-9 and KDHE Bulletin 4-2, 'Minimum Standards for Design and Construction of Onsite Wastewater Systems' (March 1997), Table 7, read 2026-10-20.
- These figures are the state agency's minimum standard (KDHE Bulletin 4-2); most Kansas counties have their own sanitary code, which governs where it exists.
- The bulletin also recommends larger sizes than the minimum: 1,350 gallons for up to three bedrooms.
Kansas 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 | 1,800 gal | — |
The first step up comes at 4 bedrooms, from 1,000 to 1,200 gallons, and a six-bedroom house needs 1,800 gallons. Beyond the table the rule adds 300 gallons for each extra bedroom. These are minimums: the permit can call for more, and a bigger tank needs pumping less often.
How Kansas compares with nearby states
Iowa requires 1,250 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; South Dakota requires 1,000 gallons for three bedrooms. 37 of the 47 states listed here share Kansas's three-bedroom figure.
Before you size a tank in Kansas
- 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 Kansas'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.