Glossary

Baffle: A barrier inside the septic tank controlling flow between compartments and keeping solids from migrating into the drain field. R.61-56 requires inlet and outlet baffles on tanks.

Certification / Approval to Operate: SCDES approval issued after the final construction inspection passes, authorizing the system to be used.

Critical Area Line: The coastal jurisdictional boundary used in setback measurement. Setbacks from tidal waters are measured from the mean high water elevation or the critical area line.

DHEC: The South Carolina Department of Health and Environmental Control, which handled septic permitting until July 1, 2024. It no longer exists — its environmental programs, including onsite wastewater, moved to SCDES.

Drain Field: Where treated effluent disperses into soil for final treatment. Sized according to percolation rates and soil conditions, using approved aggregate such as gravel or synthetic media.

DPH: The South Carolina Department of Public Health, created alongside SCDES in the July 2024 split. It took the public health programs; it does not handle septic permitting.

Effluent: The liquid leaving the septic tank after solids settle out. Under R.61-56.301 it may not be discharged to the ground surface or any water body without a permit.

Engineered System: A system designed by a Registered Professional Engineer for a site that conventional standards cannot accommodate — commonly required where the water table is high or the lot is in the coastal zone.

Final Construction Inspection: SCDES inspection before the system is backfilled, verifying the installation matches the permitted design. Except for engineer-designed systems, installers must arrange it with the Department in advance.

Mean High Water Elevation: The reference point for measuring setbacks from tidal waters, alongside the critical area line.

Net Liquid Capacity: The working volume of a septic tank. Under R.61-56.201 no tank may be installed with a net liquid capacity below 1,000 gallons.

Onsite Wastewater System: The regulatory term in South Carolina for what most homeowners call a septic system. Governed by S.C. Code Regs. R.61-56.

Percolation Rate: How quickly water moves through soil. Drain field sizing is calculated from percolation rates alongside soil conditions and daily wastewater flow estimates.

Permit to Construct: SCDES authorization required before installing an onsite wastewater system. The Department may also require one for repair, relocation or replacement of a system or its components.

Pollution Control Act: The South Carolina statute under which septic violations can be penalized. Penalties can reportedly reach $10,000 per day.

R.61-56: S.C. Code Regs. R.61-56, Onsite Wastewater Systems — the regulation governing septic in South Carolina, covering site conditions, tank standards, construction criteria, discharge and permitting. Updated in 2022.

Remote Subsurface Wastewater Infiltration Area: A drain field located off the parcel served. Requires an easement allowing ingress and egress for construction and operation.

Riser: An extension bringing a buried tank access lid to grade. Typically $200 to $400, and it pays for itself within about two pump-outs by removing the excavation charge.

SCDES: The South Carolina Department of Environmental Services, created July 1, 2024 from the split of DHEC. It handles septic permitting, site evaluations, contractor licensing and enforcement. Septic sits under its Bureau of Regional and Laboratory Services.

Setback: The minimum required distance between a septic component and a well, property line, surface water body or structure, set out in Table 1 of R.61-56.

Site Evaluation: SCDES assessment of soil and site conditions determining what system a property can support. The applicant must prepare the lot beforehand under R.61-56.104.

Stub-Out: The point where plumbing exits the building to connect to the septic system. Its proposed location must be marked before the site evaluation.

Tier 1 Installer: The installer licensing level covering most standard residential installations. South Carolina reportedly uses a three-tier system under R.61-56, and homeowner self-installation is not permitted.