section .0800 – tank capacity, leak testing, and installation requirements

15A ncac 18e .0801      SEPTIC TANK CAPACITY REQUIREMENTs

(a)  Minimum liquid capacities for septic tanks shall be in accordance with the following:

(1)           The minimum capacity of any septic tank shall be 1,000 gallons unless otherwise provided for in this Rule.

(2)           The minimum capacity of any septic tank serving an individual dwelling unit with five bedrooms or less shall be sized as set forth in Table XIV.

TABLE XIV. Minimum septic tank liquid capacity for dwelling units

Number of bedrooms	Minimum liquid capacity in gallons
4 or less	1,000
5	1,250

(3)           Septic tanks for dwelling units greater than five bedrooms, multiple dwelling units, places of business, or places of public assembly shall be sized in accordance with Table XV.

(4)           The minimum septic tank capacity serving two or more dwelling units shall be 1,500 gallons.

TABLE XV. Septic tank capacity for facilities not listed in Table XIV

Design daily flow in gpd (Q)	Minimum septic tank liquid capacity (V) calculation in gallons
Q ≤ 600	V = 2Q
600 < Q < 1,500	V = 1.17Q + 500
1,500 ≤ Q ≤ 4,500	V = 0.75Q + 1,125
Q > 4,500	V = Q

(5)           Septic tanks for RWTS and PIA Systems shall be sized in accordance with the RWTS or PIA Approval, pursuant to Sections .1500 and .1700 of this Subchapter.

(b)  The minimum liquid capacity requirements of Paragraph (a) of this Rule shall be met by use of a single two compartment tank or by two tanks installed in series. The tanks in series may be constructed with or without a baffle wall. Each tank shall have a minimum liquid capacity of 1,000 gallons.

(c)  When a grinder pump or sewage lift pump is installed prior to the septic tank, the required septic tank liquid capacity as set forth in this Rule shall be doubled. The minimum liquid capacity may be met by installing two or more septic tanks in series, each tank containing two compartments. The minimum liquid capacity of each tank shall be 1,000 gallons.

(d)  The Department shall review other septic tanks designed to receive wastewater from grinder pumps or sewage lift pumps if designed by a PE to ensure that effluent discharged from the septic tank meets DSE as set forth in Table III of Rule .0402(a) of this Subchapter.

(e)  An effluent filter approved in accordance with Rule .1404 of this Subchapter shall be in the outlet of the final compartment of the septic tank.

(f)  When two or more tanks are used in series in accordance with Paragraphs (b) or (c) of this Rule, the following conditions shall be met:

(1)           the outlet of the initial tank shall consist of an outlet sanitary tee extending down 25 to 50 percent of the liquid depth; and

(2)           an approved effluent filter shall be in the outlet of the final compartment.

History Note:        Authority G.S. 130A-334; 130A-335(e), (f), and (f1);

Eff. January 1, 2024.