The License Level South Carolina
Requires for Commercial Work

A watertight tank holds solids while liquid soaks into the soil, where microbes finish the treatment. That much is the same as a house. What changes on a commercial site is the sizing basis and the hardware. Design flow comes off an occupancy table — 40 gallons per seat per day for a full-service restaurant, 15 per employee per shift for an office, 100 per hotel room — not off bedrooms. South Carolina draws a hard line at 1,500 gallons per day: below it is a small system, above it is a large system that a South Carolina licensed professional engineer must design. Commercial systems also add parts a house never needs — a grease trap ahead of the tank for any kitchen, duplex pumps, pressure-dosed distribution — because commercial waste is stronger and arrives in sharper peaks.

A lot of the ground we work never gets sewer — rural Pickens, Oconee, and Anderson, the outer edges of Greenville County, and most of the mountain and farm country over the lines in North Carolina and Georgia — so any new build out there starts here. The trigger that catches owners out is change of use: South Carolina regulation requires a new permit to construct before any alteration that increases flow or changes the character of the wastewater. A retail bay at 15 gallons per employee becoming a restaurant at 40 gallons per seat can multiply the design flow tenfold and push the project over the engineering threshold overnight. Also worth knowing before you plan anything — South Carolina prohibits new septic permits, and even repairs, where a sewer treatment facility is "accessible for connection." The county or municipality decides what counts as accessible, and if connecting would require annexation or an easement across someone else’s land, it is not considered accessible.

We quote commercial systems from the soil report, not from a price list, and we would treat anyone who does otherwise with suspicion — the soil dictates the size of the field, and the field dominates the cost. Design flow sets the tank and the pumps. Soil acceptance rate sets the trench footage, and on Piedmont red clay that footage is the entire conversation. In South Carolina the state fees are published and firm: a site evaluation fee, a treatment facility construction permit fee, a pump station permit fee, and an annual fee to operate a land application permit. Those are yours regardless of who installs the system, and we carry the current schedule into the estimate. On schedule, a straightforward commercial system on decent soil is a one to three month permitting exercise. A large system using low pressure pipe or drip distribution is a six to nine month exercise before you break ground, because the land application permit carries a 180-day statutory review clock that runs first. Once issued, a South Carolina onsite permit is good for five years. North Carolina and Georgia permit onsite systems through their own state and county health programs, with their own fees and their own clocks, so the first thing we pin down is which state the parcel is in — the design changes with it.

Three facts change everything about this work on our home ground, and two of them are South Carolina law specifically. First, South Carolina requires backhoe pits above the Fall Line that separates the Piedmont from the Coastal Plain — Pickens, Greenville, Oconee, and Anderson all sit above it, so every site evaluation up here needs an excavator on site, unlike the Lowcountry. Second, South Carolina does not use percolation tests at all; the word does not appear in the regulation. Sizing is done on soil morphology by certified staff or a licensed soil classifier. Out-of-state developers routinely arrive asking for a perc test — and North Carolina and Georgia do evaluate and permit onsite systems their own way, which is exactly why the answer depends on which side of the line your parcel sits. Third, the geology does not care about state lines. Red clay is expensive everywhere in the Piedmont: sand accepts 0.9 to 1.0 gallons per square foot per day, while clay accepts 0.1 to 0.4. A 600-gallon-per-day office needs about 200 feet of trench on sand and roughly 1,000 feet on our clay — five times the field, plus a 50% reserve area on top. South Carolina even publishes a system standard written specifically for expansive Piedmont clay, using the weathered saprolite below it.