Ohio · Ohio Administrative Code Chapter 3701-29
The Ohio Department of Health writes the rule and local health districts issue permits, with authority to add requirements.
Minimum tank
One to three bedroom dwelling.
Design flow
Held two days for settling.
Cost index
Regional labour and permits.
Sets the design flow and the legal minimum.
Code sizes on bedrooms, not people.
Used to size the matching drainfield. Unsure? Sandy loam is the common default.
Glacial till across the north and west with slow-percolating silty clay loam and a seasonal perched water table. Unglaciated southeastern Ohio has thin soil over shale and steep slopes.
Ohio's rule expects secondary treatment on many sites. Aerobic units, sand filters, drip distribution and mounds are all in regular use, and a plain tank-and-trench system is less dominant here than in states with better soil.
| Dwelling | Design flow | Minimum tank | With disposal |
|---|---|---|---|
| 1 bedroom | 300 gpd | 1,000 gal | 1,250 gal |
| 2 bedrooms | 300 gpd | 1,000 gal | 1,250 gal |
| 3 bedrooms | 450 gpd | 1,000 gal | 1,250 gal |
| 4 bedrooms | 600 gpd | 1,250 gal | 1,500 gal |
| 5 bedrooms | 750 gpd | 1,500 gal | 1,750 gal |
Ohio requires a site and soil evaluation, and local health districts operate an operation and maintenance program with permit renewals and periodic service reporting — an ongoing obligation rather than a one-time approval.
The state sets a floor. These Ohio counties are where the largest septic populations sit, and where local requirements most often exceed it.
| County | What makes it different |
|---|---|
| Franklin | Columbus fringe; till soils |
| Delaware | Rapid growth north of Columbus |
| Medina | Suburban development on tight soils |
| Licking | Growth corridor east of Columbus |
| Clermont | Cincinnati area with slope and soil constraints |
| Athens | Unglaciated southeast; thin soil, steep ground |
A three-bedroom home at 150 gallons per bedroom produces 450 gallons per day of design flow. On sandy loam that needs roughly 750 square feet of absorption area. On clay loam it rises to about 2,250 square feet, and on clay a conventional field is usually not permitted at all. Run your own soil class through the drainfield calculator.
Ohio's operation and maintenance program requires periodic service and reporting to the health district for many system types. Use the pump schedule calculator to work out the interval for your tank size and household.
Regional labour and permit costs in Ohio run about 96% of the national baseline. Here is what typical installations land at for a three-bedroom home:
| System type | Typical installed cost in Ohio | When it applies |
|---|---|---|
| Conventional gravity | $8,600 – $15,400 | Good soil, adequate depth to water |
| Chamber system | $9,500 – $17,700 | Alternative to gravel trenches |
| Mound system | $16,300 – $32,300 | Shallow water table or thin soil |
| Aerobic treatment | $13,800 – $27,700 | Clay soil or small lots |
| Tank pump-out (service) | $310 – $620 | Every 3–5 years |
Replacing an existing system costs more than these figures — old-system removal and re-permitting add to every line. The replacement cost calculator covers that case, and the cost estimator adjusts all of the above for your bedroom count and soil.
Verify before you build. The figures above are state minimums compiled for planning, drawn from Ohio Administrative Code Chapter 3701-29, Household Sewage Treatment Systems. County and health district rules routinely exceed them, code text changes, and only Ohio Department of Health — Sewage Treatment Systems or your local health department can confirm what applies to your parcel.
Send your sizing numbers to installers who work under Ohio rules every day.