18-29-914 Relief Vents – Stacks of More Than 10 Branch Intervals.

18-29-914.1 Where required.

   Soil and waste stacks in buildings having more than 10 branch intervals shall be provided with a relief vent at each tenth interval installed, beginning with the top floor.

18-29-914.2 Size and connection.

   The size of the relief vent shall be equal to the size of the vent stack to which it connects. The lower end of each relief vent shall connect to the soil or waste stack through a wye below the horizontal branch serving the floor, and the upper end shall connect to the vent stack through a fitting not less than 42 inches (1067 mm) above the floor.

(Amend Coun. J. 11-8-12, p. 38872, § 370; Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 5)

18-29-915 Vents for Stack Offsets.

18-29-915.1 Vent for horizontal offset of drainage stack.

   Horizontal offsets of drainage stacks shall be vented where five or more branch intervals are located above the offset. The offset shall be vented by venting the upper section of the drainage stack and the lower section of the drainage stack.

(Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 6)

18-29-915.2 Upper section.

   The upper section of the drainage stack shall be vented as a separate stack with a vent stack connection installed in accordance with Section 18-29-903.4. The offset shall be considered the base of the stack.

18-29-915.3 Lower section.

   The lower section of the drainage stack shall be vented by a yoke vent connecting between the offset and the next lower horizontal branch. The yoke vent connection shall be permitted to be a vertical extension of the drainage stack. The size of the yoke vent and connection shall be a minimum of the size required for the vent stack of the drainage stack.

18-29-916 Vent Pipe Sizing.

18-29-916.1 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 18-29-916.1
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 b

1 1/2 b

2

2 1/2

3

4

5

6

8

10

12

1 1/4 1 1/2 1 1/2

2 8 10

30 50 30

– 150 100

–

–

–

–

–

–

–

–

–

2 2 2 1/2

12 20 42

– 30 26

75 50 30

200 150 100

– – 300

–

–

–

–

–

–

–

3 3 3

10 21 53

–

42 32 27

150 110 94

360 270 230

1,040 810 680

–

–

–

–

–

–

3 4 4

102 43 140

–

25 – –

86 35 27

210 85 65

620 250 200

– 980 750

–

–

–

–

–

4 4 5

320 540 190

–

–

23 21 –

55 50 28

170 150 82

640 580 320

– – 990

–

–

–

–

5 5 5

490 940 1,400

–

–

–

21 18 16

63 53 49

250 210 190

760 670 590

–

–

–

–

6 6 6

500 1,100 2,000

–

–

–

–

33 26 22

130 100 84

400 310 260

1,000 780 660

–

–

–

6 8 8

2,900 1,800 3,400

–

–

–

–

20 – –

77 31 24

240 95 73

600 240 190

– 940 729

–

–

8 8 10

5,600 7,600 4,000

–

–

–

–

–

20 18 –

62 56 31

160 140 78

610 560 310

– – 960

–

10 10 10

7,200 11,000 15,000

–

–

–

–

–

–

24 20 18

60 51 46

240 200 180

740 630 571

–

12 12 12

7,300 13,000 20,000

–

–

–

–

–

–

–

31 24 20

120 94 79

380 300 250

940 720 610

12 15 15

26,000 15,000 25,000

–

–

–

–

–

–

–

18 – –

72 40 31

230 130 96

500 310 240

15 15

38,000 50,000

–

–

–

–

–

–

–

–

26 24

81 74

200 180

 

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.

b.   Not permitted for water closets.

(Amend Coun. J. 3-27-02, p. 82090, § 3; Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)