Septic tank size by state / East North Central
Ohio septic tank size
In Ohio the minimum septic tank for a three-bedroom house is 1,500 gallons, rising to 2,000 gallons at four bedrooms. The figure comes from OAC 3701-29-12(C)(1). That is 500 gallons more than the 1,000-gallon median of the 47 states listed here.
What the Ohio rule says
The rule is OAC 3701-29-12(C)(1), administered by Ohio Department of Health (administered by local health districts). In its own words:
Minimum liquid capacities: (a) One to two bedrooms - one thousand gallons in one or two compartments. (b) Three bedrooms - one thousand five hundred gallons in two tanks or compartments. (c) Four to five bedrooms - two thousand gallons in two tanks or compartments. (d) Six or more bedrooms - two thousand five hundred gallons plus an additional two hundred fifty gallons of tank capacity for each bedroom in two tanks or compartments.
Source: OAC 3701-29-12(C)(1), read 2026-10-20.
- At three bedrooms Ohio requires 1,500 gallons, in two tanks or two compartments.
- One and two-bedroom homes need 1,000 gallons; four and five bedrooms 2,000.
- The six-bedroom wording is ambiguous, so this site does not compute it; ask the local health district.
Ohio minimum tank size by bedrooms
| Bedrooms | Minimum tank | Versus the median state |
|---|---|---|
| 1 | 1,000 gal | same |
| 2 | 1,000 gal | — |
| 3 | 1,500 gal | +500 |
| 4 | 2,000 gal | +800 |
| 5 | 2,000 gal | +500 |
| 6 | See note | — |
The rule's six-bedroom wording is ambiguous, so the six-bedroom size is not computed here.
The first step up comes at 3 bedrooms, from 1,000 to 1,500 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 Ohio compares with nearby states
Illinois requires 1,000 gallons for three bedrooms; Indiana requires 1,000 gallons for three bedrooms; Michigan sets no statewide figure. 1 of the 47 states listed here share Ohio's three-bedroom figure.
Before you size a tank in Ohio
- 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 Ohio'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.