Drain, Waste, and Vent DWV

Sanitary Drainage Systems

Reference text for the sanitary drainage area. Every rule below is written from the printed line of

the 2024 International Plumbing Code (IPC 2024) that carries it, and each rule names the section it

comes from. Where the printed line does not state a value, no value is stated here.

1. General

The chapter governs the materials, design, construction and installation of sanitary drainage systems

(IPC 2024, 701.1). Sanitary drainage piping from plumbing fixtures in buildings, and sanitary drainage

piping systems from premises, must be connected to a public sewer; where a public sewer is not

available they must be connected to a private sewage disposal system in compliance with state or local

requirements, and, where such requirements do not exist, to an approved private sewage disposal system

in accordance with the International Private Sewage Disposal Code (IPC 2024, 701.2). The exception

covers piping and systems that convey only the discharge from bathtubs, showers, lavatories, clothes

washers and laundry trays, provided they are connected to a system in accordance with Chapter 13 or 14

(IPC 2024, 701.2, Exception).

A building having plumbing fixtures installed and intended for human habitation, occupancy or use on

premises abutting on a street, alley or easement in which there is a public sewer must have a separate

connection with the sewer; where located on the same lot, multiple buildings may connect to a common

building sewer that connects to the public sewer (IPC 2024, 701.3). Sewage or other waste deleterious

to surface or subsurface waters must not be discharged into the ground or into any waterway unless

first rendered innocuous through an approved form of treatment (IPC 2024, 701.4), and waste

detrimental to the public sewer system or to the functioning of the sewage-treatment plant must be

treated and disposed of in accordance with Section 1003 as directed by the code official (IPC 2024,

701.5). The sanitary drainage system is tested in accordance with Section 312 (IPC 2024, 701.6), and

engineered sanitary drainage systems must conform to Sections 316 and 713 (IPC 2024, 701.7).

2. Materials and joints

Sections 702.1 (above-ground sanitary drainage and vent pipe), 702.2 (underground building sanitary

drainage and vent pipe), 702.3 (building sewer pipe) and 702.4 (fittings) publish the materials and

the standards for those applications. Where the wastewater temperature will be greater than 140°F

(60°C), the sanitary drainage piping material must be rated for the highest temperature of the

wastewater (IPC 2024, 702.5). Section 702.6 governs chemical waste systems and Section 702.7 lead

bends and traps.

Section 705 contains the provisions applicable to joints specific to sanitary drainage piping

(IPC 2024, 705.1): 705.2 ABS plastic, 705.3 cast iron, 705.4 concrete joints, 705.5 copper pipe,

705.6 copper tubing, 705.7 borosilicate glass joints, 705.8 steel, 705.9 lead, 705.10 PVC plastic,

705.11 vitrified clay, 705.12 polyethylene plastic pipe, 705.13 polyolefin plastic, 705.14

polyvinylidene fluoride plastic, 705.15 polypropylene plastic, 705.16 joints between different

materials, 705.17 drainage slip joints, 705.18 caulking ferrules, 705.19 soldering bushings and

705.20 stainless steel drainage systems. Prohibited joints and connections in

drainage piping are: cement or concrete joints; mastic or hot-pour bituminous joints; joints made

with fittings not approved for the specific installation; joints between different diameter pipes made

with elastomeric rolling O-rings; solvent-cement joints between different types of plastic pipe except

where provided for in Section 705.16.4; and saddle-type fittings (IPC 2024, 707.1).

3. Building sewer

The proximity of a sewer to a water service must comply with Section 603.2 (IPC 2024, 703.1). Where a

building sewer or building drain is installed on filled or unstable ground, the drainage pipe must

conform to one of the standards for ABS plastic pipe, cast-iron pipe, copper or copper-alloy tubing,

PVC plastic pipe or polypropylene plastic pipe indicated in Table 702.3 (IPC 2024, 703.2). Where

separate systems of sanitary drainage and storm drainage are installed in the same property, the

sanitary and storm building sewers or drains may be laid side by side in one trench (IPC 2024, 703.3).

Where the entire sanitary drainage system of an existing building is replaced, existing building

drains under concrete slabs and existing building sewers that will serve the new system must be

internally examined to verify that the piping is sloping in the correct direction, is not broken, is

not obstructed and is sized for the drainage load of the new plumbing drainage system to be installed

(IPC 2024, 703.4). Cleanouts on building sewers are located as indicated in Section 708 (IPC 2024,

703.5), and where the public sewer is a combined system for both sanitary and storm water the sanitary

sewer must be connected independently to the public sewer (IPC 2024, 703.6).

4. Drainage piping installation

4.1 Slope

Horizontal drainage piping must be installed in uniform alignment at uniform slopes. The slope must be

not less than Table 704.1 shows, except that where the drainage piping is upstream of a grease

interceptor the slope must be not less than 1/4 inch per foot (2 percent slope) (IPC 2024, 704.1).

For SI: 1 inch = 25.4 mm, 1 inch per foot = 83.33 mm/m. Slopes for piping draining to a grease

interceptor comply with Section 704.1 (IPC 2024, Table 704.1, footnote a).

4.2 Size reduction, offsets and future fixtures

The size of the drainage piping must not be reduced in the direction of flow. The following are not

considered a reduction in size in the direction of flow: a 4-inch by 3-inch (102 mm by 76 mm) water

closet flange; a water closet bend fitting having a 4-inch (102 mm) inlet and a 3-inch (76 mm) outlet,

provided the 4-inch leg of the fitting is upright and below, but not necessarily directly connected

to, the water closet flange; and an offset closet flange (IPC 2024, 704.2).

Horizontal branches must connect to the bases of stacks at a point located not less than 10 times the

diameter of the drainage stack downstream from the stack, and must connect to horizontal stack offsets

at a point located not less than 10 times the diameter of the drainage stack downstream from the

upper stack (IPC 2024, 704.3). Drainage piping for future fixtures must terminate with an approved cap

or plug (IPC 2024, 704.4).

5. Connections and fittings

Connections and changes in direction of the sanitary drainage system must be made with approved

drainage fittings; connections between drainage piping and fixtures conform to Section 405 (IPC 2024,

706.1). Fittings must not have ledges, shoulders or reductions capable of retarding or obstructing

flow in the piping, and threaded drainage pipe fittings must be of the recessed drainage type; the

section does not apply to tubular waste fittings used to convey vertical flow upstream of the trap

seal liquid level of a fixture trap (IPC 2024, 706.2).

Fittings must be installed to guide sewage and waste in the direction of flow, and changes in

direction must be made by fittings installed in accordance with Table 706.3. Change in direction by

combination fittings, side inlets or increasers must be installed in accordance with Table 706.3 based

on the pattern of flow created by the fitting. Double sanitary tee patterns must not receive the

discharge of back-to-back water closets and fixtures or appliances with pumping action discharge;

back-to-back water closet connections to double sanitary tees are permitted where the horizontal

developed length between the outlet of the water closet and the connection to the double sanitary tee

pattern is 18 inches (457 mm) or greater (IPC 2024, 706.3 and Exception).

Table 706.3 — fittings for change in direction ("X" = permitted):

Fitting limitations, as the printed table carries them on the marked cells (IPC 2024,

Table 706.3, footnotes a, b and c): the fittings marked a are only permitted for a 2-inch or smaller

fixture drain; the cell marked b carries "three inches or larger"; and the double sanitary tee

limitation is Section 706.3.

Heel-inlet quarter bends are an acceptable means of connection except where the quarter bend serves a

water closet; a low-heel inlet must not be used as a wet-vented connection; side-inlet quarter bends

are an acceptable means of connection for drainage, wet venting and stack venting arrangements

(IPC 2024, 706.4).

6. Cleanouts

Cleanouts must be provided for drainage piping in accordance with Sections 708.1.1 through 708.1.12

(IPC 2024, 708.1). The principal requirements:

100 feet (30 480 mm), and building drains must have cleanouts at intervals of not more than 100 feet

(30 480 mm) except where manholes are used instead of cleanouts, in which case the manholes must be

located at intervals of not more than 400 feet (122 m); the interval is measured from the cleanout

or manhole opening, along the developed length of the piping, to the next drainage fitting providing

access for cleaning, the end of the horizontal drain or the end of the building drain (IPC 2024,

708.1.1).

100 feet (30 480 mm); building sewers 8 inches (203 mm) and larger must have a manhole located not

more than 200 feet (60 960 mm) from the junction of the building drain and building sewer and at

intervals of not more than 400 feet (122 m) (IPC 2024, 708.1.2).

the junction or within 10 feet (3048 mm) of the developed length of piping upstream of the

junction; removal of the water closet must not be required to provide cleanout access (IPC 2024,

708.1.3).

direction greater than 45 degrees, a cleanout must be installed at the change of direction; where

more than one such change occurs within 40 feet (12 192 mm) of developed length, the cleanout

installed for the first change serves all changes in direction within that 40 feet (IPC 2024,

708.1.4).

4 inches (102 mm) need not be larger than 4 inches (102 mm); a removable P-trap with slip or ground

joint connections can serve as a cleanout for drain piping one size larger than the P-trap size;

cleanouts located on stacks can be one size smaller than the stack size; and the size of cleanouts

for cast-iron piping can be in accordance with the referenced standards for cast-iron fittings in

Table 702.4 (IPC 2024, 708.1.5 and Exceptions).

acceptable as a cleanout equivalent (IPC 2024, 708.1.6). Cleanout plugs must be of copper-alloy,

plastic or other approved materials (borosilicate glass for borosilicate glass piping systems),

copper-alloy plugs conforming to ASTM A74 and limited to metallic piping systems, plastic plugs

conforming to the referenced standards for plastic pipe fittings in Table 702.4, with a raised

square head, a countersunk square head or a countersunk slot head, and manufactured with a blind

end threaded hole where a trim cover screw will be installed (IPC 2024, 708.1.7).

must have gas-tight covers that require tools for removal (IPC 2024, 708.1.8). The installation

arrangement of a cleanout must enable cleaning of drainage piping only in the direction of drainage

flow, except for test tees serving as cleanouts and a two-way cleanout installation approved for

meeting Section 708.1.3 (IPC 2024, 708.1.9).

less than 18 inches (457 mm) from, and perpendicular to, the face of the opening to any

obstruction; cleanouts for 8-inch (203 mm) and larger piping must have a clearance of not less than

36 inches (914 mm) (IPC 2024, 708.1.10).

inside of plenums, within walls, within floor/ceiling assemblies, below grade and in crawl spaces

where the height from the crawl space floor to the nearest obstruction along the path from the

crawl space opening to the cleanout is less than 24 inches (610 mm). Cleanouts with openings at a

finished wall must have the face of the opening within 1 1/2 inches (38 mm) of the finished wall

surface; cleanouts located below grade must be extended to grade level so that the top of the

cleanout plug is at or above grade; and a cleanout installed in a floor or walkway without a trim

cover must have a countersunk plug installed so the top surface of the plug is flush with the

finished surface of the floor or walkway (IPC 2024, 708.1.11).

trim cover fasteners that thread into cleanout plugs must be corrosion resistant, and cleanout plugs

must not be covered with mortar, plaster or any other permanent material (IPC 2024, 708.1.11.1).

Cleanout assemblies in accordance with ASME A112.36.2M must be installed where it is necessary to

protect a cleanout plug from the loads of vehicular traffic (IPC 2024, 708.1.11.2).

where another cleanout of equal size is installed with the required access and clearance (IPC 2024,

708.1.12).

7. Fixture units

Drainage fixture unit values in Table 709.1 designate the relative load weight of different kinds of

fixtures, to be used in estimating the total load carried by a soil or waste pipe and in connection

with Tables 710.1(1) and 710.1(2) (IPC 2024, 709.1).

Table notes that carry rules: a showerhead over a bathtub or whirlpool bathtub attachment does not

increase the drainage fixture unit value (footnote b); trap size must be consistent with the fixture

outlet size (footnote d); and for traps larger than 3 inches, Table 709.2 is used (footnote a).

Showers are rated on the total flow rate through showerheads and body sprays: 5.7 gpm or less = 2 dfu

with a 1 1/2-inch trap; greater than 5.7 gpm to 12.3 gpm = 3 dfu with a 2-inch trap; greater than

12.3 gpm to 25.8 gpm = 5 dfu with a 3-inch trap; greater than 25.8 gpm to 55.6 gpm = 6 dfu with a

4-inch trap (IPC 2024, Table 709.1).

Where discharges to a waste receptor or to a drainage system are known only in gallons per minute, the

drainage fixture unit values for those flows are computed on the basis that 1 gpm (0.06 L/s) of flow

is equivalent to two drainage fixture units (IPC 2024, 709.3). The drainage fixture unit load of an

indirect waste receptor receiving the discharge of indirectly connected fixtures is the sum of the

drainage fixture unit values of the fixtures that discharge to the receptor, but not less than the

value given for the indirect waste receptor in Table 709.1 or 709.2 (IPC 2024, 709.4). Waste receptors

such as floor drains, floor sinks and hub drains that receive only clear-water waste from display

cases, refrigerated display cases, ice bins, coolers and freezers have a drainage fixture unit value

of one-half (IPC 2024, 709.4.1).

8. Drainage system sizing

The maximum number of drainage fixture units connected to a given size of building sewer, building

drain or horizontal branch of the building drain is determined using Table 710.1(1), and the maximum

number connected to a given size of horizontal branch or vertical soil or waste stack is determined

using Table 710.1(2) (IPC 2024, 710.1).

Table 710.1(1) — building drains and sewers:

The minimum size of any building drain serving a water closet is 3 inches (IPC 2024,

Table 710.1(1), footnote a).

9. Offsets in drainage piping in buildings of five stories or more

If a horizontal branch connects to the stack within 2 feet (610 mm) above or below a vertical stack

offset, and the offset is located more than four branch intervals below the top of the stack, the

offset must be vented in accordance with Section 907; those vents are not required where the stack and

its offset are sized as a building drain (IPC 2024, 711.1 and 711.1.1).

A stack with a horizontal offset located more than four branch intervals below the top of the stack

must be vented in accordance with Section 907 and sized as follows: the portion of the stack above

the offset is sized as for a vertical stack based on the total number of drainage fixture units above

the offset; the offset is sized in accordance with Section 710.1.1; and the portion of the stack below

the offset is sized as for the offset or based on the total number of drainage fixture units on the

entire stack, whichever is larger (IPC 2024, 711.2). Those vents are not required where the stack and

its offset are one pipe size larger than required for a building drain and the entire stack and offset

are not less in cross-sectional area than that required for a straight stack plus the area of an

offset vent as provided in Section 907 (IPC 2024, 711.2.1).

Where a vertical offset occurs in a soil or waste stack below the lowest horizontal branch, a change

in diameter of the stack because of the offset is not required; if a horizontal offset occurs below

the lowest horizontal branch, the required diameter of the offset and of the stack below it must be

determined as for a building drain in accordance with Table 710.1(1) (IPC 2024, 711.3).

10. Sumps and ejectors

Building subdrains that cannot be discharged to the sewer by gravity flow must be discharged into a

tightly covered and vented sump from which the liquid is lifted and discharged into the building

gravity drainage system by automatic pumping equipment or other approved method; in other than

existing structures, the sump must not receive drainage from any piping within the building capable of

being discharged by gravity to the building sewer (IPC 2024, 712.1). A check valve and a full-open

valve located on the discharge side of the check valve must be installed in the pump or ejector

discharge piping between the pump or ejector and the gravity drainage system, with access to such

valves; they must be located above the sump cover required by Section 712.1 or, where the discharge

pipe from the ejector is below grade, accessibly outside the sump below grade in an access pit with a

removable access cover (IPC 2024, 712.2).

The sump pit must be not less than 18 inches (457 mm) in diameter and not less than 24 inches (610 mm)

in depth unless otherwise approved, provided with access, located so that all drainage flows into the

pit by gravity, constructed of tile, concrete, steel, plastic or other approved materials, with a

solid bottom providing permanent support for the pump, and fitted with a gastight removable cover

installed not more than 2 inches (51 mm) below grade or floor level, adequate to support anticipated

loads; the sump pit is vented in accordance with Chapter 9 (IPC 2024, 712.3.2). The effluent level

control must be adjusted and maintained to at all times prevent the effluent in the sump from rising

to within 2 inches (51 mm) of the invert of the gravity drain inlet into the sump (IPC 2024, 712.3.4).

Discharge pipe and fittings must be constructed of copper or copper-alloy, CPVC, ductile iron, PE or

PVC, rated for the maximum system operating pressure and temperature, compatible with the pipe

material, and suitable for burial where buried in the earth (IPC 2024, 712.3.3.1 and 712.3.3.2).

Pumps connected to the drainage system must connect to a building sewer, building drain, soil stack,

waste stack or horizontal branch drain; where the discharge line connects into horizontal drainage

piping, the connection must be made through a wye fitting into the top of the drainage piping, and

that wye fitting must be located not less than 10 pipe diameters from the base of any soil stack,

waste stack or fixture drain (IPC 2024, 712.3.5).

A sewage pump or sewage ejector must automatically discharge the contents of the sump to the building

drainage system (IPC 2024, 712.4). Macerating toilet systems must comply with ASME A112.3.4/CSA B45.9

and be installed in accordance with the manufacturer's instructions (IPC 2024, 712.4.1). A sewage pump

or ejector must have the capacity and head for the application requirements: pumps or ejectors that

receive the discharge of water closets must be capable of handling spherical solids with a diameter of

up to and including 2 inches (51 mm), and other pumps or ejectors must be capable of handling

spherical solids up to and including 1/2 inch (13 mm). Capacity based on the diameter of the discharge

pipe must be not less than Table 712.4.2 shows; grinder pumps or grinder ejectors that receive the

discharge of water closets must have a discharge opening of not less than 1 1/4 inches (32 mm), and

macerating toilet assemblies that serve single water closets must have a discharge opening of not less

than 3/4 inch (19.1 mm) (IPC 2024, 712.4.2 and Exceptions).

11. Computerized drainage design, backwater valves and rehabilitation

The sizing, design and layout of the drainage system may be designed by approved computer design

methods; the load is computed from the simultaneous or sequential discharge conditions from fixtures,

appurtenances and appliances or the peak usage design condition; discharge profiles for flow rates

versus time follow the manufacturer's specifications; pipe must be sized to prevent full-bore flow;

pipe size calculations use the pipe wall roughness factor (ks) per the manufacturer's specifications

as modified for aging roughness factors with deposits and corrosion; and horizontal drainage piping

must be designed and installed at slopes in accordance with Table 704.1 (IPC 2024, 713.1, 713.2,

713.2.1, 713.3, 713.3.1 and 713.3.2).

Where plumbing fixtures are installed on a floor with a finished floor elevation below the elevation

of the manhole cover of the next upstream manhole in the public sewer, such fixtures must be protected

by a backwater valve installed in the building drain or horizontal branch serving such fixtures;

fixtures installed on a floor with a finished floor elevation above the elevation of that manhole

cover must not discharge through a backwater valve, except that in existing buildings fixtures above

that elevation are not prohibited from discharging through a backwater valve (IPC 2024, 714.1 and

Exception). Backwater valves must comply with ASME A112.14.1, CSA B181.1 or CSA B181.2 (IPC 2024,

714.2), and must be installed so that access is provided to the working parts (IPC 2024, 714.3).

Sections 715 through 718 govern vacuum drainage systems, replacement of underground building sewers

and building drains by pipe-bursting methods, relining of building sewers and building drains, and

rehabilitation of building sewers and building drains; vacuum drainage systems must be designed per

the manufacturer's instructions and the plans, specifications and other data submitted to the code

official for review and approval prior to installation (IPC 2024, 715.1, 715.2, 716.1, 717.1 and

718.1).

12. Testing the sanitary drainage system

Section 312 governs the tests (IPC 2024, 701.6):

openings in the piping tightly closed except the highest opening, the system filled with water to

the point of overflow; if tested in sections, each opening tightly plugged except the highest

openings of the section under test and each section filled with water, but no section tested with

less than a 10-foot (3048 mm) head of water; in testing successive sections, not less than the upper

10 feet of the next preceding section must be tested, so that no joint or pipe in the building,

except the uppermost 10 feet of the system, is submitted to a test of less than a 10-foot head of

water. The pressure must be held for not less than 15 minutes, and the system must then be tight at

all points (IPC 2024, 312.2).

forcing air into the system until there is a uniform gauge pressure of 5 psi (34.5 kPa) or enough

to balance a 10-inch (254 mm) column of mercury, held for not less than 15 minutes, with adjustments

for ambient temperature or gasket seating made before the test period begins (IPC 2024, 312.3).

uniform gauge pressure of negative 5 pounds per square inch or a negative 10 inches of mercury

column, held without removal of additional air for 15 minutes (IPC 2024, 312.4).

and in sufficient detail to determine compliance; where a smoke test is used it is made by filling

all traps with water and introducing into the entire system a pungent, thick smoke produced by one

or more smoke machines; when the smoke appears at stack openings on the roof, the stack openings

must be closed and a pressure equivalent to a 1-inch water column (248.8 Pa) held for a test period

of not less than 15 minutes (IPC 2024, 312.5).

Vents and Venting

Reference text for the venting area. Every rule below is written from the printed line of the

2024 International Plumbing Code (IPC 2024) that carries it, and each rule names the section it comes

from. Where the printed line does not state a value, no value is stated here.

1. General

The chapter governs the materials, design, construction and installation of vent systems (IPC 2024,

901.1). The plumbing system must be provided with a system of vent piping that permits the admission

or emission of air so that the seal of any fixture trap is not subjected to a pressure differential of

more than 1 inch of water column (249 Pa) (IPC 2024, 901.2), and traps and trapped fixtures must be

vented in accordance with one of the venting methods specified in the chapter (IPC 2024, 901.2.1).

The purpose stated by the code for the whole chapter: the proper operation of a gravity flow drainage

system depends on maintaining an air path throughout the system, to prevent waste and odor blow back

into fixtures and siphoning of the trap seal in fixture traps (IPC 2024, Chapter 9, About this

chapter).

The vent system for a chemical waste drainage system must be independent of any sanitary drainage vent

system; its termination must be through the roof to the outdoors or to an air admittance valve

complying with ASSE 1049, and air admittance valves for chemical waste drainage systems must be

constructed of one of the materials indicated in Table 702.6 and be tested for chemical resistance in

accordance with ASTM F1412 (IPC 2024, 901.3). The plumbing vent system must not be used for purposes

other than the venting of the plumbing system (IPC 2024, 901.4). The vent system is tested in

accordance with Section 312 (IPC 2024, 901.5), and engineered venting systems must conform to

Section 919 (IPC 2024, 901.6).

2. Materials

Materials and methods for venting systems comply with the applicable provisions of Section 702

(IPC 2024, 902.1). For a chemical waste drainage vent system, pipe and fitting materials follow

Section 702.6 and the construction and installation methods follow the pipe and fitting manufacturer's

instructions (IPC 2024, 902.1.1).

Flashing materials carry their own weights: sheet copper for vent pipe flashings must conform to

ASTM B152 and weigh not less than 8 ounces per square foot (2.5 kg/m²) (IPC 2024, 902.2), and sheet

lead for vent pipe flashings must weigh not less than 3 pounds per square foot (15 kg/m²) for

field-constructed flashings and not less than 2 1/2 pounds per square foot (12 kg/m²) for

prefabricated flashings (IPC 2024, 902.3).

3. Vent terminals

The vent pipe must terminate by extending to the outdoors through the roof or the side wall in

accordance with one of the methods of Sections 903.1.1 through 903.1.4 (IPC 2024, 903.1).

this document does not carry a numeric height on that line (IPC 2024, 903.1.1).

deck, or for similar purposes, open vent pipes must terminate not less than 7 feet (2134 mm) above

the roof (IPC 2024, 903.1.2).

(such as a solar collector or photovoltaic panel mounted over the vent opening) or a roof element

(such as an architectural feature or a decorative shroud), the vent pipe must terminate not less

than 2 inches (51 mm) above the roof surface. Such roof elements must be designed to prevent the

adverse effects of snow accumulation and wind on the function of the vent. The placement of a panel

over a vent pipe, and the design of a roof element covering it, must provide an open area for the

vent pipe to the outdoors not less than the area of the pipe as calculated from the inside diameter

of the pipe, and such vent terminals must be protected by a method that prevents birds and rodents

from entering or blocking the vent pipe opening (IPC 2024, 903.1.3).

line and 10 feet (3048 mm) above the highest adjacent grade within 10 feet (3048 mm) horizontally of

the vent terminal. They must not terminate under the overhang of a structure with soffit vents, and

sidewall vent terminals must be protected to prevent birds and rodents from entering or blocking the

vent opening (IPC 2024, 903.1.4).

Frost closure and cold climate: where the 97.5 percent value for outdoor design temperature is 0°F

(-18°C) or less, vent extensions through a roof or wall must be not less than 3 inches (76 mm) in

diameter, and any increase in the size of the vent must be made not less than 1 foot (305 mm) inside

the thermal envelope of the building (IPC 2024, 903.2). 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 must be protected against freezing by insulation, heat or both (IPC 2024, 903.6).

The juncture of each vent pipe with the roof line must be made watertight by an approved flashing

(IPC 2024, 903.3), and a vent terminal must not be used for any purpose other than a vent terminal

(IPC 2024, 903.4).

Location: an open vent terminal from a drainage system must not be located directly beneath any door,

openable window, or other air intake opening of the building or of an adjacent building, and such a

vent terminal must not be within 10 feet (3048 mm) horizontally of such an opening unless it is

3 feet (914 mm) or more above the top of that opening (IPC 2024, 903.5).

4. Outdoor vent extensions

The vent system serving each building drain must have not less than one vent pipe that extends to the

outdoors (IPC 2024, 904.1). That required vent must be a dry vent connecting to the building drain or

to an extension of a drain that connects to the building drain, and must not be an island fixture vent

as allowed by Section 916 (IPC 2024, 904.1.1). It must be sized in accordance with Section 906.2

based on the required size of the building drain (IPC 2024, 904.1.2).

A vent stack is required for every drainage stack that has five branch intervals or more, except for

drainage stacks installed in accordance with Section 913 (IPC 2024, 904.2). Vent stacks or stack vents

must terminate outdoors to the open air or to a stack-type air admittance valve in accordance with

Section 918 (IPC 2024, 904.3). Vent stacks must connect to the base of the drainage stack, at or below

the lowest horizontal branch; where the vent stack connects to the building drain, the connection must

be located downstream of the drainage stack and within a distance of 10 times the diameter of the

drainage stack (IPC 2024, 904.4).

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 must be sized in accordance with Section 906.1, with the number of

fixture units equal to the sum of all fixture units on all stacks connected to the header, and the

developed length equal to 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 (IPC 2024,

904.5).

5. Vent connections and grades

Individual, branch and circuit vents must connect to a vent stack, stack vent, air admittance valve or

extend to the open air (IPC 2024, 905.1). Vent and branch vent pipes must be graded and connected so

as to drain back to the drainage pipe by gravity (IPC 2024, 905.2). Every dry vent connecting to a

horizontal drain must connect above the centerline of the horizontal drain pipe (IPC 2024, 905.3).

Every dry vent must 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 (IPC 2024, 905.4); the exception is vents for

interceptors located outdoors. A connection between a vent pipe and a vent stack or stack vent must be

made at not less than 6 inches (152 mm) above the flood level rim of the highest fixture served by the

vent, and horizontal vent pipes forming branch vents, relief vents or loop vents must be located not

less than 6 inches (152 mm) above the flood level rim of the highest fixture served (IPC 2024, 905.5).

Where drainage piping has been roughed-in for future fixtures, a rough-in connection for a vent must

be installed, of a size not less than one-half the diameter of the rough-in drain to be served; the

vent rough-in must connect to the vent system or be vented by other means provided for in the chapter,

and the connection must be identified to indicate that it is a vent (IPC 2024, 905.6).

6. Vent pipe sizing

6.1 Stack vents and vent stacks

The minimum required diameter of stack vents and vent stacks is determined from the developed length

and the total drainage fixture units connected to them in accordance with Table 906.1; in no case

may the diameter be less than one-half the diameter of the drain served, or less than 1 1/4 inches

(32 mm) (IPC 2024, 906.1). Table 906.1 is a grid of maximum developed length of vent per soil or waste

stack diameter, total fixture units being vented and vent diameter; the value is read at the

intersection of those conditions (IPC 2024, Table 906.1).

6.2 Vents other than stack vents or vent stacks

The diameter of individual vents, branch vents, circuit vents and relief vents must be not less than

one-half the required diameter of the drain served, with the required size of the drain determined in

accordance with Table 710.1(2). Vent pipes must be not less than 1 1/4 inches (32 mm) in diameter.

Vents exceeding 40 feet (12 192 mm) in developed length must be increased by one nominal pipe size for

the entire developed length of the vent pipe, and relief vents for soil and waste stacks in buildings

having more than 10 branch intervals are sized in accordance with Section 908.2 (IPC 2024, 906.2).

The developed length of individual, branch, circuit and relief vents is 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 (IPC 2024, 906.3). Where multiple branch vents are

connected to a common branch vent, the common branch vent must be sized on the basis of the size of

the common horizontal drainage branch that is, or would be, required to serve the total drainage

fixture unit load being vented (IPC 2024, 906.4).

Sump vents: drainage piping below sewer level must be vented in the same manner as that of a gravity

system, and building sump vent sizes for sumps with sewage pumps or sewage ejectors, other than

pneumatic, are determined in accordance with Table 906.5.1 (IPC 2024, 906.5.1).

7. Vents for stack offsets and relief vents

Horizontal offsets of drainage stacks must be vented where five or more branch intervals are located

above the offset; the offset is vented by venting the upper section and the lower section of the

drainage stack (IPC 2024, 907.1). The upper section must be vented as a separate stack with a vent

stack connection installed in accordance with Section 904.4, and the offset is considered to be the

base of the stack (IPC 2024, 907.2). The lower section must be vented by a yoke vent connecting

between the offset and the next lower horizontal branch; the yoke vent connection may be a vertical

extension of the drainage stack, and the size of the yoke vent and connection must be not less than

the size required for the vent stack of the drainage stack (IPC 2024, 907.3).

Soil and waste stacks in buildings having more than 10 branch intervals must be provided with a relief

vent at each tenth interval installed, beginning with the top floor (IPC 2024, 908.1). The size of the

relief vent must be equal to the size of the vent stack to which it connects; the lower end of each

relief vent must connect to the soil or waste stack through a wye below the horizontal branch serving

the floor, and the upper end must connect to the vent stack through a wye not less than 3 feet

(914 mm) above the floor (IPC 2024, 908.2).

8. Fixture vents

Each fixture trap must 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 of Table 909.1;

the developed length of the fixture drain from the trap weir to the vent fitting is not limited for

self-siphoning fixtures, such as water closets (IPC 2024, 909.1 and Exception).

The total fall in a fixture drain due to pipe slope must not exceed the diameter of the fixture drain,

and the vent connection to a fixture drain, except for water closets, must not be below the weir of

the trap (IPC 2024, 909.2). A vent must not be installed within two pipe diameters of the trap weir

(IPC 2024, 909.3).

9. Individual and common vents

Each trap and trapped fixture may be provided with an individual vent, which must connect to the

fixture drain of the trap or trapped fixture being vented (IPC 2024, 910.1). An individual vent may

vent two traps or trapped fixtures as a common vent, provided the traps or trapped fixtures being

common vented are located on the same floor level (IPC 2024, 911.1). Where the fixture drains being

common vented connect at the same level, the vent connection must be at the interconnection of the

fixture drains or downstream of the interconnection (IPC 2024, 911.2). Where the fixture drains

connect at different levels, the vent must connect as a vertical extension of the vertical drain; the

vertical drain pipe connecting the two fixture drains is considered to be the vent for the lower

fixture drain and must be sized in accordance with Table 911.3, and the upper fixture must not be a

water closet (IPC 2024, 911.3).

10. Wet venting

Any combination of fixtures within two bathroom groups located on the same floor level may be vented

by a horizontal wet vent. The wet vent is considered to be the vent for the fixtures and must 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 must

connect independently to the horizontal wet vent; only the fixtures within the bathroom groups may

connect to the wet-vented horizontal branch drain, and any additional fixtures must discharge

downstream of the horizontal wet vent (IPC 2024, 912.1).

Any combination of fixtures within two bathroom groups on the same floor level may also be vented by a

vertical wet vent, which extends from the connection of the dry vent down to the lowest fixture drain

connection, each wet-vented fixture connecting independently. Water closet drains must connect at the

same elevation, other fixture drains must connect above or at the same elevation as the water closet

fixture drains, and the dry-vent connection to the vertical wet vent must be an individual or common

vent serving one or two fixtures (IPC 2024, 912.1.1).

The dry-vent connection for a horizontal wet-vent system must be an individual vent or a common vent

for any bathroom group fixture, except an emergency floor drain; where the dry-vent connects to a

water closet fixture drain, the drain must connect horizontally to the horizontal wet-vent system, and

not more than one wet-vented fixture drain may discharge upstream of the dry-vented fixture drain

connection (IPC 2024, 912.2.1). For a vertical wet-vent system, the dry-vent connection must be an

individual vent or common vent for the most upstream fixture drain (IPC 2024, 912.2.2).

The dry vent serving the wet vent must be sized on the basis of the largest required diameter of pipe

within the wet-vent system served by the dry vent, and the wet vent must be of a size not less than

Table 912.3 specifies, based on the fixture unit discharge to the wet vent (IPC 2024, 912.3).

11. Waste stack vent

A waste stack is considered to be a vent for all of the fixtures discharging to the stack where

installed in accordance with Section 913 (IPC 2024, 913.1). The waste stack must be vertical, and both

horizontal and vertical offsets are prohibited between the lowest fixture drain connection and the

highest fixture drain connection; fixture drains must connect separately to the waste stack, and the

stack must not receive the discharge of water closets or urinals (IPC 2024, 913.2).

A stack vent must be provided for the waste stack, of a size not less than the size of the waste

stack. Offsets are permitted in the stack vent, must be located not less than 6 inches (152 mm) above

the flood level of the highest fixture and must be in accordance with Section 905.2; the stack vent

may connect with other stack vents and vent stacks in accordance with Section 904.5 (IPC 2024, 913.3).

The waste stack must be sized on the basis of the total discharge to the stack and the discharge

within a branch interval in accordance with Table 913.4, and must be the same size throughout its

length (IPC 2024, 913.4).

12. Circuit venting

Not more than eight fixtures connected to a horizontal branch drain may be circuit vented. Each

fixture drain must connect horizontally to the horizontal branch being circuit vented, and the

horizontal branch drain is classified as a vent from the most downstream fixture drain connection to

the most upstream fixture drain connection to the horizontal branch (IPC 2024, 914.1). Circuit-vented

horizontal branch drains may be connected together, each group of not more than eight fixtures being

considered a separate circuit vent conforming to the section (IPC 2024, 914.1.1).

The circuit vent connection must be located between the two most upstream fixture drains; the vent

must connect to the horizontal branch and be installed in accordance with Section 905, and the circuit

vent pipe must not receive the discharge of any soil or waste (IPC 2024, 914.2). The slope of the vent

section of the horizontal branch drain must be not greater than one unit vertical in 12 units

horizontal (8.3 percent slope), and the entire length of the vent section of the horizontal branch

drain must be sized for the total drainage discharge to the branch (IPC 2024, 914.3). Each separate

circuit-vented horizontal branch that is interconnected must be sized independently, and the

downstream circuit-vented horizontal branch must be sized for the total discharge into the branch,

including the upstream branches and the fixtures within the branch (IPC 2024, 914.3.1).

A relief vent must 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 (IPC 2024, 914.4). The relief vent must connect to the horizontal

branch drain between the stack and the most downstream fixture drain of the circuit vent, and be

installed in accordance with Section 905 (IPC 2024, 914.4.1); it may be a fixture drain or fixture

branch for fixtures located within the same branch interval as the circuit-vented horizontal branch,

and the maximum discharge to a relief vent is four fixture units (IPC 2024, 914.4.2). Fixtures other

than the circuit-vented fixtures may discharge to the horizontal branch drain, provided they are

located on the same floor as the circuit-vented fixtures and are either individually or common vented

(IPC 2024, 914.5).

13. Combination waste and vent system

A combination waste and vent system must not serve fixtures other than floor drains, sinks, lavatories

and drinking fountains, and must not receive the discharge from a clinical sink (IPC 2024, 915.1). The

only vertical pipe of the system is the connection between the fixture drain and the horizontal

combination waste and vent pipe, and that vertical distance must not exceed 8 feet (2438 mm)

(IPC 2024, 915.2). The slope of a horizontal combination waste and vent pipe must not exceed one-half

unit vertical in 12 units horizontal (4 percent slope) and must be not less than Table 704.1

indicates (IPC 2024, 915.2.1).

The size of a combination waste and vent pipe must be not less than Table 915.2.2 indicates, and the

horizontal length of the system is unlimited (IPC 2024, 915.2.2):

The system must be provided with a dry vent connected at any point within the system, or must connect

to a horizontal drain that serves vented fixtures located on the same floor; combination waste and

vent systems connecting to building drains receiving only the discharge from one or more stacks must

be provided with a dry vent. The vent connection to the combination waste and vent pipe must extend

vertically to a point not less than 6 inches (152 mm) above the flood level rim of the highest fixture

being vented before offsetting horizontally (IPC 2024, 915.2.3). The vent must be sized for the total

drainage fixture unit load in accordance with Section 906.2 (IPC 2024, 915.2.4), and the fixture

branch or drain must connect to the combination waste and vent within a distance specified in

Table 909.1, the combination waste and vent pipe being considered to be the vent for the fixture

(IPC 2024, 915.2.5).

14. Island fixture venting

Island fixture venting is not 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, may be vented in accordance with Section 916 (IPC 2024, 916.1). The island

fixture vent must connect to the fixture drain as required for an individual or common vent; it must

rise vertically to above the drainage outlet of the fixture being vented before offsetting horizontally

or vertically downward, and the vent or branch vent for multiple island fixture vents must 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 (IPC 2024, 916.2).

The part of the vent located below the flood level rim of the fixture being vented must be installed

as required for drainage piping in accordance with Chapter 7, except for sizing: it is sized in

accordance with Section 906.2, its lowest point must connect full size to the drainage system, and the

connection must be to a vertical drain pipe or to the top half of a horizontal drain pipe. Cleanouts

must be provided in the island fixture vent to permit rodding of all vent piping located below the

flood level rim of the fixtures, and rodding in both directions must be permitted through a cleanout

(IPC 2024, 916.3).

15. Single-stack vent system

A drainage stack serves 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 are the vents for the drainage

system, and the drainage stack must have a stack vent (IPC 2024, 917.1). Drainage stacks must be sized

in accordance with Table 917.2, uniformly sized on the basis of the total connected drainage fixture

unit load; the stack vent must be the same size as the drainage stack, and a 3-inch (76 mm) stack

serves not more than two water closets (IPC 2024, 917.2).

NP = not permitted (IPC 2024, Table 917.2).

Horizontal branches connecting to a single-stack vent system must be sized in accordance with

Table 710.1(2); not more than one water closet may 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, and

where a water closet is within 18 inches measured horizontally from the stack and not more than one

fixture with a drain size of not more than 1 1/2 inches (38 mm) connects to a 3-inch horizontal

branch, the branch drain connection to the stack must be made with a sanitary tee (IPC 2024, 917.3).

Length of horizontal branches: water closet connections must be not greater than 4 feet (1219 mm) in

developed length measured horizontally from the stack, or 8 feet (2438 mm) where the connection is

made with a sanitary tee (IPC 2024, 917.4.1 and Exception); fixtures other than water closets must be

located not greater than 12 feet (3657 mm) in developed length, measured horizontally from the stack

(IPC 2024, 917.4.2); and the length of vertical piping in a fixture drain connecting to a horizontal

branch is not counted in computing the fixture's distance in developed length measured horizontally

from the stack (IPC 2024, 917.4.3).

The vertical portion of piping in a fixture drain to a horizontal branch must be 2 inches (51 mm); the

minimum size of the vertical portion of piping for a water-supplied urinal or standpipe must be

3 inches (76 mm); the maximum vertical drop is 4 feet (1219 mm); and fixture drains that are not

increased in size, or that have a vertical drop in excess of 4 feet, must be individually vented

(IPC 2024, 917.5).

Additional venting must be provided where more than one water closet discharges to a horizontal branch

and where the distance from a fixture trap to the stack exceeds the limits in Section 917.4; where

required, fixtures must be vented by individual vents, common vents, wet vents, circuit vents, or a

combination waste and vent pipe, and the dry vent extensions for that additional venting must connect

to a branch vent, vent stack, stack vent, air admittance valve, or terminate outdoors (IPC 2024,

917.6).

Stack offsets: where fixture drains are not connected below a horizontal offset in a stack, the

horizontal offset need not be vented; where horizontal branches or fixture drains are connected below

a horizontal offset in a stack, the offset must be vented in accordance with Section 907, and fixture

connections must not be made to a stack within 2 feet (610 mm) above or below a horizontal offset

(IPC 2024, 917.7). Stacks greater than 2 branch intervals in height must not receive the discharge of

horizontal branches on the lower two floors, and there must not be 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 (IPC 2024, 917.8). The building drain and building sewer receiving the

discharge of a single stack vent system must be sized in accordance with Table 710.1(1) (IPC 2024,

917.9).

16. Air admittance valves

Vent systems using air admittance valves must comply with Section 918. Stack-type air admittance

valves must conform to ASSE 1050, and individual and branch-type air admittance valves must conform to

ASSE 1051 (IPC 2024, 918.1). The valves must be installed in accordance with the section and the

manufacturer's instructions, and air admittance valves must be installed after the DWV testing

required by Section 312.2 or 312.3 has been performed (IPC 2024, 918.2).

Individual, branch and circuit vents may terminate with a connection to an individual or branch-type

air admittance valve (IPC 2024, 918.3), and stack vents and vent stacks may terminate to stack-type

air admittance valves (IPC 2024, 918.3). Individual and branch-type air admittance valves must 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 must be provided with a relief vent connecting to a vent stack or stack vent, or extending

outdoors to the open air. That relief vent must connect to the horizontal branch drain between the

stack and the most downstream fixture drain connected to the horizontal branch drain, be sized in

accordance with Section 906.2, be installed in accordance with Section 905, and may serve as the vent

for other fixtures (IPC 2024, 918.3.1). Stack-type air admittance valves are prohibited from serving as

the vent terminal for vent stacks or stack vents that serve drainage stacks having more than six

branch intervals (IPC 2024, 918.3.2).

Location: individual and branch-type air admittance valves must be located not less than 4 inches

(102 mm) above the horizontal branch drain or fixture drain being vented; stack-type air admittance

valves must be located not less than 6 inches (152 mm) above the flood level rim of the highest

fixture being vented; the valve must be located within the maximum developed length permitted for the

vent and installed not less than 6 inches (152 mm) above insulation materials (IPC 2024, 918.4).

Access must be provided to all air admittance valves, and such valves must be installed in a location

that allows air to enter the valve (IPC 2024, 918.5). The valve must be rated in accordance with the

standard for the size of the vent to which it is connected (IPC 2024, 918.6), and within each plumbing

system not less than one stack vent or vent stack must extend outdoors to the open air (IPC 2024,

918.7).

Prohibited installations: air admittance valves must not be installed in nonneutralized special waste

systems as described in Chapter 8 except where such valves comply with ASSE 1049, are constructed of

materials approved in accordance with Section 702.5, and are tested for chemical resistance in

accordance with ASTM F1412; they must not be located in spaces used as supply or return air plenums;

they must not be used to vent sumps or tanks except where the vent system for the sump or tank has been

designed by an engineer; and they must not be installed on outdoor vent terminals for the sole purpose

of reducing clearances to gravity air intakes or mechanical air intakes (IPC 2024, 918.8).

17. Engineered vent systems

Engineered vent systems must comply with Section 919 and with the design, submittal, approval,

inspection and testing requirements of Section 316 (IPC 2024, 919.1). The maximum developed length of

individual fixture vents to vent branches and vent headers is determined in accordance with

Table 919.2 for the minimum pipe diameters at the indicated vent airflow rates, with the individual

vent airflow rate determined by the equation published in the section (IPC 2024, 919.2).