Glossary

15A NCAC 18E: The North Carolina Administrative Code subchapter governing on-site wastewater systems. Effective January 1, 2024, replacing rules that had stood since 1990. It had been approved to start on October 1, 2021 until House Bill 627 (S.L. 2023-77) sent parts of it back for readoption.

AOWE (Authorized On-Site Wastewater Evaluator): A licensed professional under G.S. 90A Article 5 who can evaluate a site and permit a system as an alternative to the county process, under G.S. 130A-336.2.

Baffle: A barrier inside the septic tank controlling flow between compartments and keeping solids from reaching the dispersal field.

Bedroom: Under 18E, any room meeting the North Carolina Building Code definition of a sleeping room. This matters because your system is permitted for a specific number of them, and the code definition does not always match how a room is marketed.

CA (Construction Authorization): The second of North Carolina's three permits. It authorizes actual installation, and must be obtained after the Improvement Permit and before construction. A CA is also required before repairing an existing system.

Dispersal Field: Where treated wastewater is released into soil for final treatment. Also called a drainfield, leach field or nitrification field.

EOP (Engineered Option Permit): An alternative permitting route under G.S. 130A-336.1 where a licensed professional engineer, soil scientist or geologist designs and certifies the system instead of the county evaluating it.

Existing System Authorization: Approval for reconnecting to a previously permitted system when the new or improved facility is within the same footprint and there is no increase in design daily flow or wastewater strength.

IP (Improvement Permit): The first of North Carolina's three permits. A soil and site evaluation determines whether the property can support a system and what type. It does not authorize construction — it confirms the lot works.

LC (Limiting Condition): The soil or site feature that limits how deep a dispersal field can go — bedrock, a seasonal water table, or a restrictive horizon. Vertical separation is measured down to it.

LHD (Local Health Department): The county authority that administers septic permitting in North Carolina, across all 100 counties. Where a system crosses county lines, the LHD in the county that assesses property taxes on the facility handles it.

LTAR (Long-Term Acceptance Rate): The rate at which soil can accept effluent over time, used to size the dispersal field. Under directives implementing 18E, Improvement Permits must state the usable depth to a limiting condition for the LTAR.

NCOWCICB: The North Carolina On-Site Wastewater Contractor and Inspector Certification Board. Only NCOWCICB-certified inspectors may perform point-of-sale septic inspections, under standards in 21 NCAC 39.

NOI (Notice of Intent): Under 18E .0207 as amended in June 2026, the filing a professional engineer or AOWE makes when permitting a system through an alternative route rather than obtaining an IP and CA from the county.

OP (Operation Permit): The third of North Carolina's three permits, issued after installation and inspection. It authorizes use of the system, and can be revoked if flow or wastewater strength exceeds its conditions — which sends you back to a new IP, CA and OP.

Riser: An extension bringing a buried tank access lid up toward grade. Under 15A NCAC 18E .1402(c), tanks whose access openings sit more than six inches below finished grade need a riser over each compartment, with the cover reaching to within six inches of grade.

Setback: The minimum required distance between a septic component and a well, property line, water body, or structure.

Soil Morphology: Evaluation of soil structure, texture, consistence and color to determine wastewater suitability. North Carolina relies on morphological evaluation rather than percolation testing alone, and the 2024 rules refined the criteria.

Type IIIB System: A common residential system type with one pump. Under 15A NCAC 18E .1301 it requires inspection by county staff once every five years — scheduled by the county, not requested by the homeowner.

Vertical Separation: Under 18E, the depth beneath the dispersal field infiltrative surface down to a limiting condition. Insufficient vertical separation is one of the most common reasons a site requires an engineered system.