N.Y.C. Admin. Code § PC 906: 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.

906.3 Developed length.

The developed length of individual, branch, circuit and relief vents shall be measured from the farthest point of vent connection to the drainage system to the point of connection to the vent stack, stack vent or termination outside of the building.

906.4 Multiple branch vents.

Where multiple branch vents are connected to a common branch vent, the common branch vent shall be sized in accordance with this section based on the size of the common horizontal drainage branch that is or would be required to serve the total drainage fixture unit load being vented.

906.5 Ejector vents.

Ejector vent sizes shall be determined in accordance with Sections 906.5.1 and 906.5.2.

906.5.1 Sewage pumps and sewage ejectors other than pneumatic.

Drainage piping below sewer level shall be vented in the same manner as that of a gravity system. Building sump vent sizes for sumps with sewage pumps or sewage ejectors, other than pneumatic, shall be determined in accordance with

Table 906.5.1

. Where a building sump vent connects to a sanitary vent system, the sanitary branch vent shall be at least 3 inches (76 mm) in diameter.

Table 906.5.1 Size and Length of Sump Vents

Discharge Capacity of Pump (gpm)

Maximum Developed Length of Vent (feet)

a

Diameter of vent (inches)

1 1/4

1 1/2

2

2 1/2

3

4

10

No limit

b

No limit

No limit

No limit

No limit

No limit

20

270

No limit

No limit

No limit

No limit

No limit

40

72

160

No limit

No limit

No limit

No limit

60

31

75

270

No limit

No limit

No limit

80

16

41

150

380

No limit

No limit

100

10

c

25

97

250

No limit

No limit

150

Not permitted

10

c

44

110

370

No limit

200

Not permitted

Not permitted

20

60

210

No limit

250

Not permitted

Not permitted

10

36

132

No limit

300

Not permitted

Not permitted

10

c

22

88

380

400

Not permitted

Not permitted

Not permitted

10

c

44

210

500

Not permitted

Not permitted

Not permitted

Not permitted

24

130

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon per minute = 3.785 L/m.

a.

Developed length

plus an appropriate allowance for entrance losses and friction due to fittings, changes in direction and diameter. Suggested allowances shall be obtained from NBS Monograph 31 or other

approved

sources. An allowance of 50 percent of the

developed length

shall be assumed if a more precise value is not available.

b. Actual values greater than 500 feet.

c. Less than 10 feet.

906.5.2 Pneumatic sewage ejectors.

The air pressure relief pipe from a pneumatic sewage ejector shall be connected to an independent vent stack terminating as required for vent extensions through the roof. The relief pipe shall be sized to relieve air pressure inside the ejector to atmospheric pressure, but shall be not less than 1 1/2 inches (38 mm) in size.