ADOPTS WITH AMENDMENTS:

International Plumbing Code 2015 (IPC 2015)

Heads up: There are no amended sections in this chapter.

901.1 Scope

AMENDMENT
This section has been amended at the state or city level.
The provisions of this chapter shall govern the materials, design, construction and installation of vent systems. This chapter shall control the minimum diameter of vent pipes, circuit vents, branch vents and individual vents, and the size and length of vents and various aspects of vent stacks and stack vents. Additionally, this chapter regulates vent grades and connections, height above fixtures and relief vents for stacks and fixture traps, and the venting of sumps and sewers.
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 pressure differential of more than 1 inch of water column (249 Pa).

901.2.1 Venting Required

AMENDMENT
This section has been amended at the state or city level.
Traps and trapped fixtures shall be vented in accordance with one of the venting methods specified in this chapter. All fixtures discharging downstream from a water closet shall be individually vented except as provided in Section 911.

901.3 Chemical Waste Vent Systems

AMENDMENT
This section has been amended at the state or city level.
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 outdoors and not less than 6 inches (152 mm) above roof or parapet or to an air admittance valve that complies with ASSE 1049. Air admittance valves for chemical waste systems shall be constructed of materials approved in accordance with Section 702.5 and shall be tested for chemical resistance in accordance with ASTM F 1412.
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.

901.6 Engineered Systems

AMENDMENT
This section has been amended at the state or city level.
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 21/2 pounds per square foot (12 kg/m2) for prefabricated flashings.
Open vent pipes that extend through a roof shall be terminated not less than [NUMBER] inches (mm) above the roof. Where a roof is to be used for assembly or as a promenade, observation deck, sunbathing deck or similar purposes, open vent pipes shall terminate not less than 7 feet (2134 mm) above the roof.

903.2 Frost Closure

AMENDMENT
This section has been amended at the state or city level.

903.3 Flashings

AMENDMENT
This section has been amended at the state or city level.
The juncture of each vent pipe with the roof line shall be made water tight by an approved flashing. Vent extensions in walls and soffits shall be made weather tight by caulking.

903.4 Prohibited Use

AMENDMENT
This section has been amended at the state or city level.
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.

903.5 Location of Vent Terminal

AMENDMENT
This section has been amended at the state or city level.
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 or property line, and any such vent terminal shall not be within 10 feet (3048 mm) horizontally of such an opening unless it is 2 feet (610 mm) or more above the top of such opening.
Vent terminals extending through the wall shall terminate at a point not less than 10 feet (3048 mm) from a lot line and not less than 10 feet (3048 mm) above average ground level. Vent terminals shall not terminate under the overhang of a structure with soffit vents. Side wall vent terminals shall be protected to prevent birds or rodents from entering or blocking the vent opening.

903.7 Extension Outside a Structure

AMENDMENT
This section has been amended at the state or city level.

904.1 Required Vent Extension

AMENDMENT
This section has been amended at the state or city level.

904.1 Stack Required

AMENDMENT
This section has been amended at the state or city level.
Every building in which plumbing is installed shall have at least one stack the size of which is not less than one-half of the required diameter of the building drain, and not less than 2 inches (51 mm) in diameter. Such stack shall run undiminished in size and as directly as possible from the building drain through to the open air or to a vent header that extends to the open air.

904.1.1 Installation

AMENDMENT
This section has been amended at the state or city level.

904.1.1 Connection to Drainage System

AMENDMENT
This section has been amended at the state or city level.
A vent stack shall connect to the building drain or to the base of a drainage stack in accordance with Section 903.4. A stack vent shall be an extension of the drainage stack. For townhouses and one- and two-family dwellings, the main vent shall connect to the building drain, building stack or branch thereof not less than 3 inches (76 mm) in size.

904.1.2 Size

AMENDMENT
This section has been amended at the state or city level.
A vent stack shall be required for every drainage stack that has five branch intervals or more.

Exception: Drainage stacks installed in accordance with Section 913.
Vent stacks or stack vents shall terminate outdoors to the open air or to a stack-type air admittance valve in accordance with Section 918.
Vent stacks 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 906.1. 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.
Individual, branch and circuit vents shall connect to a vent stack, stack vent, air admittance valve or extend to the open air.
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.

905.4 Vertical Rise of Vent

AMENDMENT
This section has been amended at the state or city level.
Every dry vent shall rise vertically to a point not less than 6 inches (152 mm) above the flood level rim of the highest trap or trapped fixture being vented.

Exceptions:
  1. Vents for interceptors located outdoors.
  2. When vents for interceptors and isolated floor drains are not located near an adjacent wall, the vent must rise 6 inches (152 mm) vertically before turning horizontally and continuing to the nearest wall. For cleaning purposes, a cleanout the same size as the vent shall be installed.
A connection between a vent pipe and a vent stack or stack vent shall be made at not less than 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 located not less than 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.

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 11/4 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)
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   75 200  
2 20 30 50 150  
21/2 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 50 150 580  
5 190 21 28 82 320 990
5 490 21 63 250 760
5 940 18 53 210 670
5 1,400 16 63 190 590
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 51 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.
  1. 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 not less than 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 908.2.
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 load being vented.
Sump 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

AMENDMENT
This section has been amended at the state or city level.
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. 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 or property line, 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.

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)
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 10 25 97 250 No limit No limit
150 Not permitted 10 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 22 88 380
400 Not permitted Not permitted Not permitted 10 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.
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 11/4 inches (32 mm) in size.
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 904.4. 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.
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.
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 909.1.
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 909.1
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.

909.3 Crown Vent Prohibited

AMENDMENT
This section has been amended at the state or city level.
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.

911.2 Connection at the Same Level

AMENDMENT
This section has been amended at the state or city 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.

911.3 Connection at Different Levels

AMENDMENT
This section has been amended at the state or city level.
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 911.3. The upper fixture shall not be a water closet or clothes washer.

TABLE 911.3 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.

912.1 Horizontal Wet Vent Permitted

AMENDMENT
This section has been amended at the state or city level.
Any combination of fixtures located on the same floor level is permitted to be vented by a 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. Each wet-vented fixture drain shall connect independently to the horizontal wet vent. A residential clothes washer drain line shall not be used as a wet vent.

912.1.1 Vertical Wet Vent Permitted

AMENDMENT
This section has been amended at the state or city level.
Any combination of fixtures 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 required dry-vent connection for wet-vented systems shall comply with Sections 912.2.1 and 912.2.2.

912.2.1 Horizontal Wet Vent

AMENDMENT
This section has been amended at the state or city level.
The dry-vent connection for a horizontal wet-vent system shall be an individual vent or a common vent for any fixture, except an emergency floor drain. Where the dry-vent connects to a water closet fixture drain, the drain shall connect horizontally to the horizontal wet-vent system.
The dry-vent connection for a vertical wet-vent system shall be an individual vent or common vent for the most upstream fixture drain.

912.3 Size

AMENDMENT
This section has been amended at the state or city level.
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 size not less than that specified in Table 912.3, based on the fixture unit discharge to the wet vent.

TABLE 912.3 WET VENT SIZE

WET VENT PIPE SIZE
(inches)
DRAINAGE FIXTURE
UNIT LOAD (dfu)
11/2 1
2 4
21/2 6
3 12
4 32

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. Fixture drains 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 not less than 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 904.5.
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 913.4. The waste stack shall be the same size throughout its length.

TABLE 913.4
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.

914.3 Slope and Size of Horizontal Branch

AMENDMENT
This section has been amended at the state or city level.
The slope of the vent section of the horizontal branch drain shall be not greater than one unit vertical in 12 units horizontal (8.3-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. Drainage discharge dfu values for horizontal fixture branches shall be reduced 50 percent in Table 710.1(2) for circuit-vented fixture branches.
Each separate circuit-vented horizontal branch that is interconnected shall be sized independently in accordance with Section 914.3. 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 circuitvented 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.

915.1 Type of Fixtures

AMENDMENT
This section has been amended at the state or city level.

915.1 Approval

AMENDMENT
This section has been amended at the state or city level.
Plans and specifications for each combination waste and vent system shall be submitted to the plumbing official, and approval shall be obtained before any installation is started.

915.2 Installation

AMENDMENT
This section has been amended at the state or city level.

915.2 Limits

AMENDMENT
This section has been amended at the state or city level.

915.2.1 Slope

AMENDMENT
This section has been amended at the state or city level.

915.2.1

AMENDMENT
This section has been amended at the state or city level.
A combination waste and vent system is limited to sinks, dishwashers, floor sinks, indirect waste receptors, floor drains or similar applications where the fixtures are not adjacent to walls or partitions. It consists of the installation of waste piping in which the trap of the fixture is not individually vented.

915.2.2 Size and Length

AMENDMENT
This section has been amended at the state or city level.

915.2.2

AMENDMENT
This section has been amended at the state or city level.
Appurtenances delivering large quantities of water or sewage (such as pumps) shall be excluded in a combination waste and vent system to ensure that adequate venting will be maintained.

915.2.3 Connection

AMENDMENT
This section has been amended at the state or city level.
The vent shall be sized for the total drainage fixture unit load in accordance with Section 906.2.
The fixture branch or fixture drain shall connect to the combination waste and vent within a distance specified in Table 909.1. The combination waste and vent pipe shall be considered the vent for the fixture.

915.3 Dishwashers

AMENDMENT
This section has been amended at the state or city level.
Dishwashers and scullery sinks in commercial buildings shall drain through a grease interceptor sized in accordance with this code, and they shall discharge into a floor sink through a minimum air gap.

915.4 General Design

AMENDMENT
This section has been amended at the state or city level.

915.4.1

AMENDMENT
This section has been amended at the state or city level.
Every waste pipe and trap in this system shall be at least two pipe sizes larger than the size required in Chapter 7, and at least two pipe sizes larger than any fixture tailpiece or connection, except that when P traps are installed above the floor, the P trap and horizontal fixture drain need not meet this requirement. The vertical waste pipe two sizes larger than the fixture outlet connection shall be extended above the floor to normal roughing height, and a cleanout shall be installed in top of the connecting waste tee. The fixture drain length shall be limited by Table 906.1. Floor sinks shall be connected through a running trap two pipe sizes larger than the sink outlet. Floor sink and waste piping from the floor sink to the trap shall be sized for the total fixture units draining thereto, based on Table 709.1, but in no case shall the line be less than 2-inch (51 mm) soil pipe when piping is underground.

915.4.2

AMENDMENT
This section has been amended at the state or city level.
A vent shall be provided at the upstream end of each branch, washed over or under by the last fixture on the branch. No vent shall take off from the horizontal waste branch at an angle of less than 45 degrees (0.785 rad) from the horizontal unless washed by a fixture. A minimum size vent shall be located at all points where branches intersect. A vent shall be located downstream from all fixtures in the system, in addition to the upstream vent, separating this system from all other systems in the building. No fixtures other than those permitted in Section 915.2 shall discharge into any branch or portion of this system.

915.4.3

AMENDMENT
This section has been amended at the state or city level.
The design of the system shall ensure that the vertical distance from fixture or drain outlet to trap weir does not exceed 24 inches (610 mm). Long runs shall be provided with additional relief vents located at intervals of not more than 100 feet (30 480 mm) to equalize pressure in the system.

915.5 Size of Vents

AMENDMENT
This section has been amended at the state or city level.
The size of vents shall be in accordance with requirements of Section 906.1 and Table 906.1, but the diameter shall be not less than one-half of the diameter of the waste pipe served.

915.6 Receptor Drain Size

AMENDMENT
This section has been amended at the state or city level.
Indirect waste receptors shall be sized for the fixture units draining thereto, regardless of other requirements of this code.
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 disposer, 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 point not less than 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 906.2. 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.

Section 917 Single Stack Vent System

AMENDMENT
This section has been amended at the state or city level.
UpCodes note: Prior to January 1, 2021, this section was titled "Single Stack Vent System (Sovent)" and subsections 917.1 to 917.9 from the 2015 IPC were not adopted.

917.1 Single-Stack Vent System Where Permitted

AMENDMENT
This section has been amended at the state or city level.
A drainage stack shall serve as a single-stack vent system where sized and installed in accordance with Sections 917.2 through 917.9. The drainage stack and branch piping shall be the vents for the drainage system. The drainage stack shall have a stack vent.
UpCodes note: Prior to January 1, 2021, this section was amended as:
"917.1 Design and installation shall be in accordance with the design criteria contained in the Copper Development Association (CDA) Handbook No. 802. Materials shall meet standards and specifications listed in Tables 702.1 and 702.4 for drain, waste and vent pipe and fittings."

917.1.1 Engineered Single Stack Systems

AMENDMENT
This section has been amended at the state or city level.
Engineered single stack systems shall be listed in accordance to the standards of the specific material utilized in the system, designed by a design professional and installed in accordance with the manufacturer's installation instructions. 

The delayed effective date of this Rule is January 1, 2021.
The Statutory authority for Rule-making is G. S. 143-136; 143-138.

917.2 Stack Size

AMENDMENT
This section has been amended at the state or city level.
Drainage stacks shall be sized in accordance with Table 917.2. Stacks shall be uniformly sized based on the total connected drainage fixture unit load. The stack vent shall be the same size as the drainage stack. A 3-inch (76 mm) stack shall serve not more than two closets.

TABLE 917.2
SINGLE STACK SIZE
STACK SIZE
(inches)
MAXIMUM CONNECTED DRAINAGE FIXTURE UNITS
Stacks less than
75 feet in height
Stacks 75 feet to
less than 160 feet
in height
Stacks 160 feet
and greater in
height
3 24 NP NP
4 225 24 NP
5 480 225 24
6 1,015 480 225
8 2,320 1,015 480
10 4,500 2,320 1,015
12 8,100 4,500 2,320
15 13,600 8,100 4,500

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
Horizontal branches connecting to a single stack vent system shall be sized in accordance with Table 710.1(2). Not more than one water closet shall discharge into a 3-inch (76 mm) horizontal branch at a point within a developed length of 18 inches (457 mm) measured horizontally from the stack.

Where a water closet is within 18 inches (457 mm) measured horizontally from the stack and not more than one fixture with a drain size of not more than 11/2 inches (38 mm) connects to a 3-inch (76 mm) horizontal branch, the branch drain connection to the stack shall be made with a sanitary tee.
The length of horizontal branches shall conform to the requirements of Sections 917.4.1 through 917.4.3.
Water closet connections shall be not greater than 4 feet (1219 mm) in developed length measured horizontally from the stack.
Exception: Where the connection is made with a sanitary tee, the maximum developed length shall be 8 feet (2438 mm).
Fixtures other than water closets shall be located not greater than 12 feet (3657 mm) in developed length, measured horizontally from the stack.
The length of vertical piping in a fixture drain connecting to a horizontal branch shall not be considered in computing the fixture's distance in developed length measured horizontally from the stack.
The vertical portion of piping in a fixture drain to a horizontal branch shall be 2 inches (51 mm). The minimum size of the vertical portion of piping for a water-supplied urinal or standpipe shall be 3 inches (76 mm). The maximum vertical drop shall be 4 feet (1219 mm). Fixture drains that are not increased in size, or have a vertical drop in excess of 4 feet (1219 mm), shall be individually vented.

917.6 Additional Venting Required

AMENDMENT
This section has been amended at the state or city level.
Additional venting shall be provided where more than one water closet discharges to a horizontal branch where the distance from a fixture trap to the stack exceeds the limits in Section 917.4. Where additional venting is required, the fixture(s) shall be vented by individual vents, common vents, wet vents, circuit vents, or a combination waste and vent pipe. The dry vent extensions for the additional venting shall connect to a branch vent, vent stack, stack vent, air admittance valve, or shall terminate outdoors.
Where fixture drains are not connected below a horizontal offset in a stack, a horizontal offset shall not be required to be vented. Where horizontal branches or fixture drains are connected below a horizontal offset in a stack, the offset shall be vented in accordance with Section 907. Fixture connections shall not be made to a stack within 2 feet (610 mm) above or below a horizontal offset.
Stacks greater than 2 branch intervals in height shall not receive the discharge of horizontal branches on the lower two floors. There shall be no connections to the stack between the lower two floors and a distance of not less than 10 pipe diameters downstream from the base of the single stack vented system.
The building drain and building sewer receiving the discharge of a single stack vent system shall be sized in accordance with Table 710.1(1).
Vent systems utilizing air admittance valves shall comply with this section. Stack-type air admittance valves shall conform to ASSE 1050. Individual and branchtype 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 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 in accordance with Section 918.3.1. Stack vents and vent stacks shall be permitted to terminate to stack-type air admittance valves in accordance with Section 918.3.2.
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. 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 906.2 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 be prohibited from serving as the vent terminal for vent stacks or stack vents that serve drainage stacks having more than 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 not less than 6 inches (152 mm) above insulation materials.
Access shall be provided to all air admittance valves. Such valves shall be installed in a location 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, not less than 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 except where such valves are in compliance with ASSE 1049, are constructed of materials approved in accordance with Section 702.5 and are tested for chemical resistance in accordance with ASTM F 1412. Air admittance valves shall not be located in spaces utilized as supply or return air plenums. Air admittance valves without an engineered design shall not be utilized to vent sumps or tanks of any type.

Section 919 Engineered Vent Systems

AMENDMENT
This section has been amended at the state or city level.

919.1 General

AMENDMENT
This section has been amended at the state or city level.

919.2 Individual Branch Fixture and Individual Fixture Header Vents

AMENDMENT
This section has been amended at the state or city level.

Section 920 Computerized Vent Design

AMENDMENT
This section has been amended at the state or city level.

920.1 Design of Vent System

AMENDMENT
This section has been amended at the state or city level.

920.2 System Capacity

AMENDMENT
This section has been amended at the state or city level.
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