Septic tank size by state / East South Central
Kentucky septic tank size
In Kentucky 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 902 KAR 10:085 Section 6(2), Table 2 'Minimum Capacity of Pretreatment Units'. That matches the 1,000-gallon median of the 47 states listed here.
What the Kentucky rule says
The rule is 902 KAR 10:085 Section 6(2), Table 2 'Minimum Capacity of Pretreatment Units'; design flow Section 6(1), Table 1, administered by Kentucky Cabinet for Health and Family Services, Department for Public Health (local health departments permit). In its own words:
Table 2 Minimum Capacity of Pretreatment Units: Number of Bedrooms | Gallon Capacity (Without Garbage Disposal) | Gallon Capacity (With Garbage Disposal): 3 or less 1,000 1,250; 4 1,250 1,500; 5 1,500 1,750; Each Additional 250 250
Source: 902 KAR 10:085 Section 6(2), Table 2 'Minimum Capacity of Pretreatment Units', read 2026-10-20.
- A garbage disposal adds 250 gallons at every size.
- Where tanks are in series, the first must hold at least 1,000 gallons.
Kentucky 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 Kentucky compares with nearby states
Alabama requires 1,000 gallons for three bedrooms; Mississippi requires 900 gallons for three bedrooms; Tennessee requires 900 gallons for three bedrooms. 37 of the 47 states listed here share Kentucky's three-bedroom figure.
Before you size a tank in Kentucky
- 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 Kentucky'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.