South Carolina · South Carolina Regulation 61-56
The South Carolina Department of Environmental Services administers the program through regional environmental health offices.
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.
Coastal plain sands in the lowcountry with a high water table, sandhills through the midlands, and piedmont clay in the upstate. Coastal counties face both water table and setback constraints.
Conventional trenches through much of the state. Coastal and lowcountry sites use fill and mound systems for separation. Advanced treatment appears where lot size or soil rules out conventional absorption.
| 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 |
South Carolina requires a site evaluation by department staff and licenses installers. Coastal counties enforce setbacks from tidal waters and OCRM critical lines in addition to septic standards.
The state sets a floor. These South Carolina counties are where the largest septic populations sit, and where local requirements most often exceed it.
| County | What makes it different |
|---|---|
| Greenville | Upstate piedmont clay, growth pressure |
| Charleston | Lowcountry; high water table, tidal setbacks |
| Horry | Myrtle Beach area; sandy but very high water table |
| York | Charlotte spillover growth |
| Beaufort | Coastal, strict environmental setbacks |
| Lexington | Midlands sandhills, generally good percolation |
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.
No statewide mandated residential interval. Use the pump schedule calculator to work out the interval for your tank size and household.
Regional labour and permit costs in South Carolina run about 92% of the national baseline. Here is what typical installations land at for a three-bedroom home:
| System type | Typical installed cost in South Carolina | When it applies |
|---|---|---|
| Conventional gravity | $8,300 – $14,700 | Good soil, adequate depth to water |
| Chamber system | $9,100 – $16,900 | Alternative to gravel trenches |
| Mound system | $15,800 – $30,900 | Shallow water table or thin soil |
| Aerobic treatment | $13,300 – $26,500 | Clay soil or small lots |
| Tank pump-out (service) | $290 – $600 | 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 South Carolina Regulation 61-56, Onsite Wastewater Systems. County and health district rules routinely exceed them, code text changes, and only South Carolina DES — Onsite Wastewater Program or your local health department can confirm what applies to your parcel.
Send your sizing numbers to installers who work under South Carolina rules every day.