Chapter 1 General Requirements

Chapter 2 Definitions

Chapter 3 General Regulations

Chapter 4 Fixtures

Chapter 5 Water Heaters

Chapter 6 Water and Supply Distribution

Chapter 7 Sanitary Drainage

Chapter 8 Indirect/Special Waste

Chapter 9 Vents

Chapter 10 Traps‚ Interceptors and Separators

Chapter 11 Storm Drainage

Chapter 12 Special Piping and Storage Systems

Chapter 13 Referenced Standards

Appendix A Reserved

Appendix B Reserved

Appendix C Gray Water Recycling Systems

Appendix D Reserved

Appendix E Sizing of Water Piping System

Appendix F Structural Safety

Appendix G Vacuum Drainage System

Appendix H Sanitary Drainage Pipe Fittings

The provisions of this chapter shall govern the materials, design, construction and installation of vent systems.
The plumbing system shall be provided with a system of vent piping that will permit the admission or emission of air so that the seal of any fixture trap shall not be subjected to a pneumatic pressure differential of more than 1 inch of water column (249 Pa).
Every trap and trapped fixture shall be vented in accordance with one of the venting methods specified in this chapter.
The vent system for a chemical waste system shall be independent of the sanitary vent system and shall terminate separately through the roof to the open air.
The plumbing vent system shall not be utilized for purposes other than the venting of the plumbing system.
The vent system shall be tested in accordance with Section 312.
Engineered venting systems shall conform to the provisions of Section 918 or Section 919.
The materials and methods utilized for the construction and installation of venting systems shall comply with the applicable provisions of Section 702.
Sheet copper for vent pipe flashings shall conform to ASTM B 152 and shall weigh not less than 8 ounces per square foot (2.5 kg/m2).
Sheet lead for vent pipe flashings shall weigh not less than 3 pounds per square foot (15 kg/m2) for field-constructed flashings and not less than 2.5 pounds per square foot (12 kg/m2) for prefabricated flashings.
The vent system serving each building drain shall have at least one vent pipe that extends to the outdoors.
The required vent shall be a dry vent that connects to the building drain or an extension of a drain that connects to the building drain. Such vent shall not be an island fixture vent as allowed by Section 913.
The required vent shall be sized in accordance with Section 916.2 based on the required size of the building drain.
A vent stack shall be required for every drainage stack that has five branch intervals or more.
Every vent stack or stack vent shall terminate outdoors to the open air or to a stack-type air admittance valve in accordance with Section 917.
Every vent stack shall connect to the base of the drainage stack. The vent stack shall connect at or below the lowest horizontal branch. Where the vent stack connects to the building drain, the connection shall be located downstream of the drainage stack and within a distance of 10 times the diameter of the drainage stack.
Stack vents and vent stacks connected into a common vent header at the top of the stacks and extending to the open air at one point shall be sized in accordance with the requirements of Section 916.1. The number of fixture units shall be the sum of all fixture units on all stacks connected thereto, and the developed length shall be the longest vent length from the intersection at the base of the most distant stack to the vent terminal in the open air, as a direct extension of one stack.
All open vent pipes that extend through a roof shall be terminated at least 18 inches (458 mm) above the roof, except that where a roof is to be used for any purpose other than weather protection, the vent extensions shall be run at least 7 feet (2134 mm) above the roof.
Every vent extension through a roof or wall shall be a minimum of 3 inches (76 mm) in diameter. Any increase in the size of the vent shall be made inside the structure a minimum of 1 foot (305 mm) below the roof.
The juncture of each vent pipe with the roof line shall be made water tight by an approved flashing.
Vent terminals shall not be used as a flag pole or to support flag poles, television aerials or similar items, except when the piping has been anchored in an approved manner.
An open vent terminal from a drainage system shall not be located directly beneath any door, openable window, or other air intake opening of the building or of an adjacent building, and any such vent terminal shall not be within 10 feet (3048 mm) horizontally of such an opening unless it is at least 2 feet (610 mm) above the top of such opening.
Vent terminals extending through the wall shall be prohibited, including above grade penetrations, except for a penthouse and except for building trap where provided. Vent terminals shall not terminate under the overhang of a structure with soffit vents. Side wall vent terminals shall be prohibited.
In climates where the 97.5-percent value for outside design temperature is less than 0°F (-18°C), vent pipes installed on the exterior of the structure shall be protected against freezing by insulation, heat or both.
All individual, branch and circuit vents shall connect to a vent stack, stack vent, air admittance valve or extend to the open air.
All vent and branch vent pipes shall be so graded and connected as to drain back to the drainage pipe by gravity.
Every dry vent connecting to a horizontal drain shall connect above the centerline of the horizontal drain pipe.
Every dry vent shall rise vertically to a minimum of 6 inches (152 mm) above the flood level rim of the highest trap or trapped fixture being vented.

Exception:
Vents for interceptors located outdoors.
A connection between a vent pipe and a vent stack or stack vent shall be made at least 6 inches (152 mm) above the flood level rim of the highest fixture served by the vent. Horizontal vent pipes forming branch vents, relief vents or loop vents shall be at least 6 inches (152 mm) above the flood level rim of the highest fixture served.
Where the drainage piping has been roughed-in for future fixtures, a rough-in connection for a vent shall be installed. The vent size shall be not less than one-half the diameter of the rough-in drain to be served. The vent rough-in shall connect to the vent system, or shall be vented by other means as provided for in this chapter. The connection shall be identified to indicate that it is a vent.
Each fixture trap shall have a protecting vent located so that the slope and the developed length in the fixture drain from the trap weir to the vent fitting are within the requirements set forth in Table 906.1.

Exception:
The developed length of the fixture drain from the trap weir to the vent fitting for self-siphoning fixtures, such as water closets, shall not be limited.

TABLE 906.1 MAXIMUM DISTANCE OF FIXTURE TRAP FROM VENT


SIZE OF TRAP
(inches)
SLOPE
(inch per foot)
DISTANCE FROM TRAP
(feet)
11/4 1/4 5
11/2 1/4 6
2 1/4 8
3 1/8 12
4 1/8 16


For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 inch per foot = 83.3 mm/m.
The total fall in a fixture drain due to pipe slope shall not exceed the diameter of the fixture drain, nor shall the vent connection to a fixture drain, except for water closets, be below the weir of the trap.
A vent shall not be installed within two pipe diameters of the trap weir.
Each trap and trapped fixture is permitted to be provided with an individual vent. The individual vent shall connect to the fixture drain of the trap or trapped fixture being vented.
An individual vent is permitted to vent two traps or trapped fixtures as a common vent. The traps or trapped fixtures being common vented shall be located on the same floor level.
Where the fixture drains being common vented connect at the same level, the vent connection shall be at the interconnection of the fixture drains or downstream of the interconnection.
Where the fixture drains connect at different levels, the vent shall connect as a vertical extension of the vertical drain. The vertical drain pipe connecting the two fixture drains shall be considered the vent for the lower fixture drain, and shall be sized in accordance with Table 908.3. The upper fixture shall not be a water closet.

TABLE 908.3 COMMON VENT SIZES


PIPE SIZE
(inches)
MAXIMUM DISCHARGE FROM UPPER
FIXTURE DRAIN (dfu)
11/2 1
2 4
21/2 to 3 6


For SI: 1 inch = 25.4 mm.
Any combination of fixtures within two bathroom groups or two single user toilet rooms located on the same floor level is permitted to be vented by a horizontal wet vent. The wet vent shall be considered the vent for the fixtures and shall extend from the connection of the dry vent along the direction of the flow in the drain pipe to the most downstream fixture drain connection to the horizontal branch drain. Only the fixtures within the bathroom groups shall connect to the wet-vented horizontal branch drain. Any additional fixtures shall discharge downstream of the horizontal wet vent.
Any combination of fixtures within two bathroom groups located on the same floor level is permitted to be vented by a vertical wet vent. The vertical wet vent shall be considered the vent for the fixtures and shall extend from the connection of the dry vent down to the lowest fixture drain connection. Each wet-vented fixture shall connect independently to the vertical wet vent. Water closet drains shall connect at the same elevation. Other fixture drains shall connect above or at the same elevation as the water closet fixture drains. The dry-vent connection to the vertical wet vent shall be an individual or common vent serving one or two fixtures.
The dry-vent connection to the wet vent shall be an individual vent or common vent to the lavatory, bidet, shower or bathtub. In vertical wet-vent systems, the most upstream fixture drain connection shall be a dry-vented fixture drain connection. In horizontal wet-vent systems, not more than one wet-vented fixture drain shall discharge upstream of the dry-vented fixture drain connection.
The dry vent serving the wet vent shall be sized based on the largest required diameter of pipe within the wet- vent system served by the dry vent. The wet vent shall be of a minimum size as specified in Table 909.3, based on the fixture unit discharge to the wet vent.

TABLE 909.3 WET VENT SIZE


WET VENT PIPE SIZE
(inches)
DRAINAGE FIXTURE UNIT LOAD
(dfu)
11/2 1
2 4
21/2 6
3 12


For SI: 1 inch = 25.4 mm.
A waste stack shall be considered a vent for all of the fixtures discharging to the stack where installed in accordance with the requirements of this section.
The waste stack shall be vertical, and both horizontal and vertical offsets shall be prohibited between the lowest fixture drain connection and the highest fixture drain connection. Every fixture drain shall connect separately to the waste stack. The stack shall not receive the discharge of water closets or urinals.
A stack vent shall be provided for the waste stack. The size of the stack vent shall be not less than the size of the waste stack. Offsets shall be permitted in the stack vent, shall be located at least 6 inches (152 mm) above the flood level of the highest fixture and shall be in accordance with Section 905.2. The stack vent shall be permitted to connect with other stack vents and vent stacks in accordance with Section 903.5.
The waste stack shall be sized based on the total discharge to the stack and the discharge within a branch interval in accordance with Table 910.4. The waste stack shall be the same size throughout its length.

TABLE 910.4 WASTE STACK VENT SIZE


STACK SIZE
(inches)
MAXIMUM NUMBER OF DRAINAGE FIXTURE UNITS (dfu)
Total discharge into one branch interval Total discharge for stack
11/2 1 2
2 2 4
21/2 No limit 8
3 No limit 24
4 No limit 50
5 No limit 75
6 No limit 100


For SI: 1 inch = 25.4 mm.
A maximum of eight fixtures connected to a horizontal branch drain shall be permitted to be circuit vented. Each fixture drain shall connect horizontally to the horizontal branch being circuit vented. The horizontal branch drain shall be classified as a vent from the most downstream fixture drain connection to the most upstream fixture drain connection to the horizontal branch.
Circuit-vented horizontal branch drains are permitted to be connected together. Each group of a maximum of eight fixtures shall be considered a separate circuit vent and shall conform to the requirements of this section.
The circuit vent connection shall be located between the two most upstream fixture drains. The vent shall connect to the horizontal branch and shall be installed in accordance with Section 905. The circuit vent pipe shall not receive the discharge of any soil or waste.
The maximum slope of the vent section of the horizontal branch drain shall be one unit vertical in 12 units horizontal (8-percent slope). The entire length of the vent section of the horizontal branch drain shall be sized for the total drainage discharge to the branch.
Each separate circuit-vented horizontal branch that is interconnected shall be sized independently in accordance with Section 911.3. The downstream circuit-vented horizontal branch shall be sized for the total discharge into the branch, including the upstream branches and the fixtures within the branch.
A relief vent shall be provided for circuit- vented horizontal branches receiving the discharge of four or more water closets and connecting to a drainage stack that receives the discharge of soil or waste from upper horizontal branches.
The relief vent shall connect to the horizontal branch drain between the stack and the most downstream fixture drain of the circuit vent. The relief vent shall be installed in accordance with Section 905.
The relief vent is permitted to be a fixture drain or fixture branch for fixtures located within the same branch interval as the circuit-vented horizontal branch. The maximum discharge to a relief vent shall be four fixture units.
Fixtures, other than the circuit-vented fixtures, are permitted to discharge to the horizontal branch drain. Such fixtures shall be located on the same floor as the circuit-vented fixtures and shall be either individually or common vented.
A combination drain and vent system shall not serve fixtures other than floor drains, sinks, lavatories and drinking fountains. Combination drain and vent systems shall not receive the discharge from a food waste grinder or clinical sink.
The only vertical pipe of a combination drain and vent system shall be the connection between the fixture drain and the horizontal combination drain and vent pipe. The maximum vertical distance shall be 8 feet (2438 mm). A combination drain and vent system sized in accordance with Table 912.3 shall be unlimited in horizontal length.
The horizontal combination drain and vent pipe shall have a maximum slope of one-half unit vertical in 12 units horizontal (4-percent slope). The minimum slope shall be in accordance with Table 704.1.
The combination drain and vent system shall be provided with a dry vent connected at any point within the system or the system shall connect to a horizontal drain that is vented in accordance with one of the venting methods specified in this chapter. Combination drain and vent systems connecting to building drains receiving only the discharge from a stack or stacks shall be provided with a dry vent. The vent connection to the combination drain and vent pipe shall extend vertically a minimum of 6 inches (152 mm) above the flood level rim of the highest fixture being vented before offsetting horizontally.
The vent shall be sized for the total drainage fixture unit load in accordance with Section 916.2.
The fixture branch or fixture drain shall connect to the combination drain and vent within a distance specified in Table 906.1. The combination drain and vent pipe shall be considered the vent for the fixture.
The minimum size of a combination drain and vent pipe shall be in accordance with Table 912.3.

TABLE 912.3 SIZE OF COMBINATION DRAIN AND VENT PIPE


DIAMETER PIPE
(inches)
MAXIMUM NUMBER OF DRAINAGE
FIXTURE UNITS (dfu)
Connecting to a
horizontal branch

or stack
Connecting to a
building drain or building subdrain
22 3 4
21/2 6 26
3 12 31
4 20 50
5 160 250
6 360 575


For SI: 1 inch = 25.4 mm.
Island fixture venting shall not be permitted for fixtures other than sinks and lavatories. Residential kitchen sinks with a dishwasher waste connection, a food waste grinder, or both, in combination with the kitchen sink waste, shall be permitted to be vented in accordance with this section.
The island fixture vent shall connect to the fixture drain as required for an individual or common vent. The vent shall rise vertically to above the drainage outlet of the fixture being vented before offsetting horizontally or vertically downward. The vent or branch vent for multiple island fixture vents shall extend to a minimum of 6 inches (152 mm) above the highest island fixture being vented before connecting to the outside vent terminal.
The vent located below the flood level rim of the fixture being vented shall be installed as required for drainage piping in accordance with Chapter 7, except for sizing. The vent shall be sized in accordance with Section 916.2. The lowest point of the island fixture vent shall connect full size to the drainage system. The connection shall be to a vertical drain pipe or to the top half of a horizontal drain pipe. Cleanouts shall be provided in the island fixture vent to permit rodding of all vent piping located below the flood level rim of the fixtures. Rodding in both directions shall be permitted through a cleanout.
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.
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 wye not less than 3 feet (914 mm) above the floor.
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.
The upper section of the drainage stack shall be vented as a separate stack with a vent stack connection installed in accordance with Section 903.4. The offset shall be considered the base of the stack.
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.
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 916.1, but in no case shall the diameter be less than one-half the diameter of the drain served or less than 11/4 inches (32 mm).

TABLE 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)
11/4 11/2 2 21/2 3 4 5 6 8 10 12
11/4 2 30
11/2 8 50 150
11/2 10 30 100
2 12 30 75 200
2 20 26 50 150
21/2 42 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 73 190 720

(continued)


TABLE 916.1
continued

SIZE AND DEVELOPED LENGTH OF STACK VENTS AND VENT STACKS


DIAMETER OF
SOIL OR

WASTE STACK
TOTAL FIXTURE
UNITS BEING

VENTED
MAXIMUM DEVELOPED LENGTH OF VENT (feet)a
DIAMETER OF VENT (inches)
11/4 11/2 2 21/2 3 4 5 6 8 10 12
(inches) (dfu)
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 46 180 570
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.
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 11/4 inches (32 mm) in diameter. Vents exceeding 40 feet (12 192 mm) in developed length shall be increased by one nominal pipe size for the entire developed length of the vent pipe. Relief vents for soil and waste stacks in buildings having more than 10 branch intervals shall be sized in accordance with Section 914.2.
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.
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 (dfu) load being vented.
Branch vents exceeding 40 feet (12 192 mm) in developed length shall be increased by one nominal size for the entire developed length of the vent pipe.
Sump vent sizes shall be determined in accordance with Sections 916.5.1 and 916.5.2.
Drainage piping below sewer level shall be vented in a similar manner to 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 916.5.1.

TABLE 916.5.1 SIZE AND LENGTH OF SUMP VENTS


DISCHARGE CAPACITY OF PUMP
(gpm)
MAXIMUM DEVELOPED LENGTH OF VENT (feet)a
Diameter of vent (inches)
11/4 11/2 2 21/2 3 4
10 No limitb 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 10c 25 97 250 No limit No limit
150 Not permitted 10c 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 10c 22 88 380
400 Not permitted Not permitted Not permitted 10c 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 NSB 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.
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 not be less than 1 1 / 4 inches (32 mm) in size.
Vent systems utilizing air admittance valves shall comply with this section. Stack-type air admittance valves shall conform to ASSE 1050. Individual and branch-type air admittance valves shall conform to ASSE 1051.
The valves shall be installed in accordance with the requirements of this section and the manufacturer’s installation instructions. Air admittance valves shall be installed after the DWV testing required by Section 312.2 or 312.3 has been performed.
Individual, branch and circuit vents shall be permitted to terminate with a connection to an individual or branch-type air admittance valve. Stack vents and vent stacks shall be permitted to terminate to stack-type air admittance valves. Individual and branch-type air admittance valves shall vent only fixtures that are on the same floor level and connect to a horizontal branch drain. The horizontal branch drain having individual and branch-type air admittance valves shall conform to Section 917.3.1 or 917.3.2. Stack-type air admittance valves shall conform to Section 917.3.3.
The horizontal branch drain shall connect to the drainage stack or building drain a maximum of four branch intervals from the top of the stack.
Where the horizontal branch is located more than four branch intervals from the top of the stack, the horizontal branch shall be provided with a relief vent that shall connect to a vent stack or stack vent, or extend outdoors to the open air. The relief vent shall connect to the horizontal branch drain between the stack and the most downstream fixture drain connected to the horizontal branch drain. The relief vent shall be sized in accordance with Section 916.2 and installed in accordance with Section 905. The relief vent shall be permitted to serve as the vent for other fixtures.
Stack-type air admittance valves shall not serve as the vent terminal for vent stacks or stack vents that serve drainage stacks exceeding six branch intervals.
Individual and branch-type air admittance valves shall be located a minimum of 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented. Stack-type air admittance valves shall be located not less than 6 inches (152 mm) above the flood level rim of the highest fixture being vented. The air admittance valve shall be located within the maximum developed length permitted for the vent. The air admittance valve shall be installed a minimum of 6 inches (152 mm) above insulation materials.
Access shall be provided to all air admittance valves. The valve shall be located within a ventilated space that allows air to enter the valve.
The air admittance valve shall be rated in accordance with the standard for the size of the vent to which the valve is connected.
Within each plumbing system, a minimum of one stack vent or vent stack shall extend outdoors to the open air.
Air admittance valves shall not be installed in nonneutralized special waste systems as described in Chapter 8. Valves shall not be located in spaces utilized as supply or return air plenums.
Engineered vent systems shall comply with this section and the design, submittal, approval, inspection and testing requirements of Section 105.4.
The maximum developed length of individual fixture vents to vent branches and vent headers shall be determined in accordance with Table 918.2 for the minimum pipe diameters at the indicated vent airflow rates.

The individual vent airflow rate shall be determined in accordance with the following:

Q
h,b = Nn,b Qv                                 (Equation 9-1)

For SI: Qh,b = Nn,b Qv (0.4719 L/s)

where:

N
n,b = Number of fixtures per header (or vent branch) ÷ total number of fixtures connected to vent stack.

Qh,b = Vent branch or vent header airflow rate (cfm).

Qv = Total vent stack airflow rate (cfm).

Qv (gpm) = 27.8 rs 2/3 (1 - rs) D8/3

Qv (cfm) = 0.134 Qv (gpm)

where:

D
   = Drainage stack diameter (inches).

Q
w = Design discharge load (gpm).

r
s   = Waste water flow area to total area.

   =


Individual vent airflow rates are obtained by equally distributing Qh,b into one-half the total number of fixtures on the branch or header for more than two fixtures; for an odd number of total fixtures, decrease by one; for one fixture, apply the full value of Qh,b.

Individual vent developed length shall be increased by 20 percent of the distance from the vent stack to the fixture vent connection on the vent branch or header.

TABLE 918.2 MINIMUM DIAMETER AND MAXIMUM LENGTH OF INDIVIDUAL BRANCH FIXTURE VENTS AND INDIVIDUAL FIXTURE HEADER VENTS FOR SMOOTH PIPES


DIAMETER OF VENT
PIPE (inches)
INDIVIDUAL VENT AIRFLOW RATE (cubic feet per minute)
Maximum developed length of vent (feet)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
1/2 95 25 13 8 5 4 3 2 1 1 1 1 1 1 1 1 1 1 1 1
3/4 100 88 47 30 20 15 10 9 7 6 5 4 3 3 3 2 2 2 2 1
1 100 94 65 48 37 29 24 20 17 14 12 11 9 8 7 7 6 6
11/4 100 87 73 62 53 46 40 36 32 29 26 23 21
11/2 100 96 84 75 65 60 54 49 45
2 100


For SI: 1 inch = 25.4 mm, 1 cubic foot per minute = 0.4719 L/s, 1 foot = 304.8 mm.
The sizing, design and layout of the vent system shall be permitted to be determined by approved computer program design methods.
The vent system shall be based on the air capacity requirements of the drainage system under a peak load condition.
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