Section PC 906: Vent Pipe Sizing

906.1 Size of stack vents and vent stacks.

The minimum required diameter of stack vents and vent stacks shall be determined from the developed length and the total of drainage fixture units connected thereto in accordance with Table 906.1, but in no case shall the diameter be less than one-half the diameter of the drain served or less than 1 1/4 inches (32 mm).

Table 906.1
Size and Developed Length of Stack Vents and Vent Stacks

Diameter of Soil or Waste Stack (inches)	Total Fixture Units Being Vented (dfu)	Maximum Developed Length of Vent (feet) a Diameter of Vent (inches)
		1 1/4	1 1/2	2	2 1/2	3	4	5	6	8	10	12
1 1/4	2	30		—	—	—	—	—	—	—	—	—
1 1/2	8	50	150
1 1/2	10	30	100
2	12		75	200		—	—	—	—	—	—	—
2	20	30	50	150
2 1/2	42	26	30	100	300
3	10	—	42	150	360	1,040	—	—	—	—	—	—
3	21		32	110	270	810
3	53		27	94	230	680
3	102	—	25	86	210	620		—	—	—	—	—
4	43			35	85	250	980
4	140			27	65	200	750
4	320	—	—	23	55	170	640		—	—	—	—
4	540			21	50	150	580
5	190				28	82	320	990
5	490	—	—	—	21	63	250	760	—	—	—	—
5	940				18	53	210	670
5	1,400				16	49	190	590
6	500	—	—	—	—	33	130	400	1,000	—	—	—
6	1,100					26	100	310	780
6	2,000					22	84	260	660
6	2,900	—	—	—	—	20	77	240	600		—	—
8	1,800						31	95	240	940
8	3,400						24	73	190	729
8	5,600	—	—	—	—	—	20	62	160	610		—
8	7,600						18	56	140	560
10	4,000							31	78	310	960
10	7,200	—	—	—	—	—	—	24	60	240	740	—
10	11,000							20	51	200	630
10	15,000							18	46	180	571
12	7,300	—	—	—	—	—	—	—	31	120	380	940
12	13,000								24	94	300	720
12	20,000								20	79	250	610
12	26,000	—	—	—	—	—	—	—	18	72	230	500
15	15,000									40	130	310
15	25,000									31	96	240
15	38,000	—	—	—	—	—	—	—	—	26	81	200
15	50,000									24	74	180

 

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.

a.   The developed length shall be measured from the vent connection to the open air.

906.2 Vents other than stack vents or vent stacks.

The diameter of individual vents, branch vents, circuit vents and relief vents shall be at least one-half the required diameter of the drain served. The required size of the drain shall be determined in accordance with Table 710.1(2). Vent pipes shall not be less than 1 1/4 inches (32 mm) in diameter. Vents shall be sized in accordance with Table 906.1 utilizing the drainage fixture units and the corresponding developed length. Relief vents for soil and waste stacks in buildings having more than 10 branch intervals shall be sized in accordance with Section 908.2.