The Governing Framework (Post-October 2021 Rewrite)

North Carolina rewrote its entire onsite wastewater rulebook effective October 1, 2021. The current authority is:

• NC General Statute §130A-335 — the governing state law.
• 15A NCAC Subchapter 18E — the administrative code (currently in effect; supersedes the older Subchapter 18A .1900 rules).
• NCDHHS On-Site Wastewater Protection Branch (OSWP) — writes and interprets the rules at the state level.
• Local Health Departments (LHDs) — administer Improvement Permits (IPs), Construction Authorizations (CAs), and Authorizations to Operate (ATOs) at the county level.

Septic Tank Capacity — Rule 18E .0801

Rule 18E .0801(a)(1) establishes the absolute minimum capacity for any septic tank:

For single-family dwellings with 5 or fewer bedrooms, the rule uses Table XIV:

For larger dwellings, multi-family, or commercial facilities (not in Table XIV), the rule switches to Table XV, which scales by design daily flow (Q) in gallons per day:

Two-Compartment or Two-Tanks-in-Series Requirement

Rule 18E .0801(b):

This is a significant departure from many states: North Carolina requires either two compartments in a single tank OR two tanks in series for every permitted installation. A single-compartment 1,000-gallon tank alone does NOT meet the current rule — it must have an internal compartment wall or be paired with a second 1,000-gallon tank in series.

Effluent Filter — Rule 18E .1404

Rule 18E .0801(e) mandates an approved effluent filter in the outlet of the final septic tank compartment:

Filter specifications are in Rule 18E .1404 — typically requiring NSF 46 certification or equivalent. The filter is the owner's responsibility to clean periodically (typically every 12–36 months).

Grinder Pump & Lift Pump Upsize Rule

If a grinder pump or sewage lift pump is installed upstream of the septic tank, Rule 18E .0801(c) requires the capacity to be doubled:

For a typical 4-bedroom home with a grinder pump, the septic tank capacity jumps from 1,000 gallons to 2,000 gallons. This is commonly satisfied by two 1,000-gallon two-compartment tanks in series. Plan for it at permit time — retrofitting after the fact is expensive.

Permit Process — IP, CA, and ATO

NC uses a three-step permit sequence:

1. Improvement Permit (IP). Pre-approval that the site meets basic soil and setback conditions. Good for 5 years (with conditions).
2. Construction Authorization (CA). Permit to build — issued after system design is approved. Required before any installation work begins.
3. Authorization to Operate (ATO). Post-installation permit issued after final inspection. This is the document that enables occupancy.

Each step involves the Local Health Department (LHD). Authorized On-Site Wastewater Evaluators (AOWEs) — private licensed professionals — can perform certain site evaluations and system design, streamlining the process. In jurisdictions that participate in the AOWE program, you may experience faster turnaround than through LHD-only review.

Material Approvals

North Carolina accepts polyethylene septic tanks that appear on the NCDHHS approved-tank list. Tanks from Norwesco, Snyder, Enduraplas, and Chem-Tainer have approved models on this list. Verify before ordering:

• Model appears on the current NCDHHS approved list (approvals are published on the OSWP website with dated updates).
• Tank has two compartments OR you're ordering two tanks in series.
• Effluent filter is NSF 46 certified or approved by the Department.
• Tank meets ASTM D1998 or equivalent for polyethylene storage tank construction.

North Carolina-Specific Considerations

• Rapid-growth counties. Wake, Mecklenburg, Guilford, Durham, and Orange counties have high-volume OSSF permitting with 4–8 week timelines. Plan ahead.
• Coastal counties. Brunswick, New Hanover, Carteret, Dare, and other coastal counties have high groundwater and may require mounded dispersal, additional setbacks from coastal waters, and anti-buoyancy anchoring for the tank.
• Mountain counties. Sloped parcels (Asheville area, Boone, etc.) commonly require Low-Pressure Pipe (LPP) dispersal or Engineered Option Permit (EOP) approaches that push projects beyond the 1,000-gallon base tank.
• Post-hurricane operations. Eastern NC counties issue post-storm inspection guidance after named events. Tanks that were submerged must be inspected and potentially pumped.

Frequently Asked Questions

Does North Carolina still use the old 15A NCAC 18A .1900 rules?

No. The current rules are 15A NCAC 18E, effective October 1, 2021. Older guides online may still reference 18A — treat those as historical only.

Can I use a 1,000-gallon single-compartment tank?

No. Rule 18E .0801(b) requires a two-compartment tank OR two tanks in series for every new installation. A single-compartment 1,000-gallon tank alone does not meet the current code.

What's the difference between an IP, CA, and ATO?

IP (Improvement Permit) confirms the site can support a system. CA (Construction Authorization) approves the specific system design and allows construction. ATO (Authorization to Operate) is the post-installation approval that enables occupancy. All three are required for a new home.

Do I need to install a lift pump if my land slopes toward the tank?

Not if gravity flow works. You only need a pump if the tank sits higher than the outlet of the dwelling or if the dispersal field requires pressurized distribution. If you DO install an upstream pump, remember that doubles the required tank capacity.

Can I use an Authorized On-Site Wastewater Evaluator (AOWE) instead of going through the LHD?

Partially. AOWEs can perform site evaluations and some design tasks, which speeds up the process. The LHD still issues the final permits but typically accepts AOWE documentation with minimal additional review.

Source Citations

• 15A NCAC Subchapter 18E (current rules, effective 2021-10-01) — PDF from NCDHHS
• NC On-Site Wastewater Protection Branch (OSWP)
• 15A NCAC 18A .1900 (historical, superseded)
• NC Session Law 2023-90 (recent OSSF legislation)