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Vents (18-29-901 et seq.)

Municipal Code of Chicago tit. 18, ch. 18-29, art. 9
in effect

Municipal Code of Chicago § 18-29-901.2 Trap seal protection.

18-29-901.2 Trap seal protection. The plumbing system shall be provided with a system of vent piping that will permit the admission or emission of air so that the seal of any fixture trap shall not be subjected to a pneumatic pressure differential of more than 1 inch (25 mm) of water (249 Pa).

Municipal Code of Chicago § 18-29-901.2.1 Venting required.

18-29-901.2.1 Venting required. Every trap and trapped fixture shall be vented in accordance with one of the venting methods specified in this chapter.

Municipal Code of Chicago § 18-29-901.3 Chemical waste vent system.

18-29-901.3 Chemical waste vent system. The vent system for a chemical waste system shall be independent of the sanitary vent system and shall terminate separately through the roof to the open air.

Municipal Code of Chicago § 18-29-901.4 Use limitations.

18-29-901.4 Use limitations. The plumbing vent system shall not be utilized for purposes other than the venting of the plumbing system, except that the waste of a fixture with a value of one fixture unit may be installed to wash out the base of a vent stack.

Municipal Code of Chicago § 18-29-901.6 Protection from freezing.

18-29-901.6 Protection from freezing. All vent pipes shall be adequately protected from freezing or adequately sized to account for frost build- up.

Municipal Code of Chicago § 18-29-902.1 Vents.

18-29-902.1 Vents. The materials and methods utilized for the construction and installation of venting systems shall comply with the applicable provisions of Section 18-29-702. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 1)

Municipal Code of Chicago § 18-29-902.2 Sheet copper.

18-29-902.2 Sheet copper. Sheet copper for vent pipe flashings shall conform to ASTM B152 and shall weigh not less than 8 ounces per square foot (2.5 kg/m 2 ).

Municipal Code of Chicago § 18-29-902.3 Sheet lead.

18-29-902.3 Sheet lead. Sheet lead for vent pipe flashings shall weigh not less than 3 pounds per square foot (15 kg/m 2 ) for field-constructed flashings and not less than 2 1/2 pounds per square foot (12 kg/m 2 ) for prefabricated flashings.

Municipal Code of Chicago § 18-29-903.1 Main vent required.

18-29-903.1 Main vent required. Every sanitary drainage system receiving the discharge of a water closet shall have a main vent that is either a vent stack or a stack vent. Such vent shall run undiminished in size and as directly as possible from the building drain through to the open air above the roof.

Municipal Code of Chicago § 18-29-903.2 Vent stack required.

18-29-903.2 Vent stack required. A vent stack or a main vent shall be installed with a soil or waste stack whenever continuous vents or other branch vents are required in two or more intervals.

Municipal Code of Chicago § 18-29-903.4 Vent connection at base.

18-29-903.4 Vent connection at base. Every vent stack shall connect to the base of the drainage stack. The vent stack shall connect at or below the lowest horizontal branch. Where the vent stack connects to the building drain, the connection shall be located within ten pipe diameters downstream of the drainage stack.

Municipal Code of Chicago § 18-29-903.5 Vent headers.

18-29-903.5 Vent headers. 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 18-29-916.1. The number of fixture units shall be the sum of all fixture units on all stacks connected thereto, and the developed length shall be the longest vent length from the intersection at the base of the most distant stack to the vent terminal in the open air, as a direct extension of one stack. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 2)

Municipal Code of Chicago § 18-29-904.1 Vent terminals required.

18-29-904.1 Vent terminals required. The vent pipe shall terminate by extending to the outdoors through the roof or the side wall in accordance with one of the methods identified in Sections 18-29-904.1.1 through 18-29-904.1.4. (Amend Coun. J. 11-8-12, p. 38872, § 369; Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 3)

Municipal Code of Chicago § 18-29-904.1.1 Roof extension unprotected.

18-29-904.1.1 Roof extension unprotected. Open vent pipes that extend through the roof shall be terminated not less than 12 inches (305 mm) above the roof. (Added Coun. J. 10-14-21, p. 37722, Art. IX, § 3)

Municipal Code of Chicago § 18-29-904.1.2 Occupiable rooftop.

18-29-904.1.2 Occupiable rooftop. Where the rooftop is to be used as a promenade, restaurant, bar, sunbathing deck, observation deck or for similar purposes (occupiable rooftop), open vent pipes shall terminate not less than 7 feet (2134 mm) above the highest walking surface located within 10 feet (3048 mm) horizontally. (Added Coun. J. 10-14-21, p. 37722, Art. IX, § 3)

Municipal Code of Chicago § 18-29-904.1.4 Sidewall vent terminal.

18-29-904.1.4 Sidewall vent terminal. Vent terminals extending through the wall shall terminate not less than 10 feet (3048 mm) from the nearest abutting lot line and 10 feet (3048 mm) above the highest adjacent grade within 10 feet (3048 mm) horizontally of the vent terminal. Vent terminals shall not terminate under the overhang of a structure with soffit vents. Sidewall vent terminals shall be protected to prevent birds and rodents from entering and blocking the vent opening. (Added Coun. J. 10-14-21, p. 37722, Art. IX, § 3; Amend Coun. J. 12-14-22, p. 58278, Art. VI, § 18)

Municipal Code of Chicago § 18-29-904.2 Frost closure.

18-29-904.2 Frost closure. Every vent extension through a roof or wall shall be a minimum of 4 inches (100 mm) in diameter. Any increase in the size of the vent shall be made a minimum of 1 foot (305 mm) inside the thermal envelope of the building. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 3)

Municipal Code of Chicago § 18-29-904.4 Prohibited use.

18-29-904.4 Prohibited use. Vent terminals shall not be used as a flag pole or to support flag poles, TV aerials or similar items, or for any purpose other than a vent terminal. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 3)

Municipal Code of Chicago § 18-29-904.5 Location of vent terminal.

18-29-904.5 Location of vent terminal. An open vent terminal from a drainage system shall not be located directly beneath a door, openable window, overhead or other ventilating intake opening of the building or of an adjacent building, nor shall any such vent terminals be within 10 feet (3.05 m) horizontally of such an opening unless the vent terminal is at least 3 feet (914 mm) above the top of such opening. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 3)

Municipal Code of Chicago § 18-29-904.6 Extension outside a structure.

18-29-904.6 Extension outside a structure. Vent pipes installed on the exterior of a structure shall be protected against freezing by insulation, heat or both. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 3)

Municipal Code of Chicago § 18-29-905.3 Vent connection to drainage system.

18-29-905.3 Vent connection to drainage system. Every dry vent connecting to a horizontal drain shall connect above the centerline of the horizontal drain pipe.

Municipal Code of Chicago § 18-29-905.4 Vertical rise of vent.

18-29-905.4 Vertical rise of vent. Every dry vent shall rise vertically to a minimum of 6 inches (150 mm) above the flood level rim of the highest trap or trapped fixture being vented.

Municipal Code of Chicago § 18-29-905.5 Height above fixtures.

18-29-905.5 Height above fixtures. A connection between a vent pipe and a vent stack or stack vent shall be made at least 6 inches (150 mm) above the flood level rim of the highest fixture served by the vent, and 42 inches (1067 mm) minimum above finished floor. Horizontal vent pipes forming branch vents, relief vents or loop vents shall be at least 6 inches (150 mm) above the flood level rim of the highest fixture served and 42 inches (1067 mm) above finished floor.

Municipal Code of Chicago § 18-29-905.7 Vent for future fixtures.

18-29-905.7 Vent for future fixtures. Where the drainage piping has been roughed-in for future fixtures, a rough-in connection for a vent shall be installed a minimum of one-half the diameter of the drain, but not less than the minimum size indicated in Table 18-29-916.1. The vent rough-in shall connect to the vent system. The connection shall be identified to indicate that the connection is a vent.

Municipal Code of Chicago § 18-29-906.1 Distance of trap from vent.

18-29-906.1 Distance of trap from vent. Each fixture trap shall have a protecting vent located so that the slope and the developed length in the fixture drain from the trap weir to the vent fitting are within the requirements set forth in Table 18-29-906.1. Exception: The developed length of the fixture drain from the trap weir to the vent fitting for self-siphoning fixtures, such as water closets, shall not be limited. Table 18-29-906.1 Maximum Distance of Fixture Trap from Vent Size of Trap (inches) | Size of Fixture Drain (inches) | Slope (inch per foot) | Distance from Trap (feet) 1 1/4 | 1 1/2 | 1/4 | 5 1 1/2 | 1 1/2 | 1/4 | 5 1 1/2 | 2 | 1/4 | 5 2 | 2 | 1/4 | 5 3 | 3 | 1/8 | 5 4 | 4 | 1/8 | 5 (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 4)

Municipal Code of Chicago § 18-29-906.2 Venting of fixture drains.

18-29-906.2 Venting of fixture drains. The vent for a fixture drain, except where serving a fixture with integral taps, such as water closets, shall connect above the weir of the fixture trap being vented.

Municipal Code of Chicago § 18-29-907.1 Individual vent permitted.

18-29-907.1 Individual vent permitted. 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.

Municipal Code of Chicago § 18-29-908.1 Individual vent as common vent.

18-29-908.1 Individual vent as common vent. 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.

Municipal Code of Chicago § 18-29-908.2 Connection at the same level.

18-29-908.2 Connection at the same 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.

Municipal Code of Chicago § 18-29-912.1 Type of fixtures.

18-29-912.1 Type of fixtures. A combination drain and vent system shall not serve fixtures other than floor drains receiving only clear water wastes. Appurtenances receiving large quantities or surges of water shall not be discharged to a combination waste and vent.

Municipal Code of Chicago § 18-29-912.2 Waste piping and trap.

18-29-912.2 Waste piping and trap. The waste piping and trap in a combination waste and an end vented (both ends) system shall be a minimum of 4 inch (100 mm) diameter. The waste piping and trap shall be at least two pipe increments larger than the pipe size required and at least two pipe increments larger than any fixture/appurtenance discharge tailpiece.

Municipal Code of Chicago § 18-29-912.2.1 Branches.

18-29-912.2.1 Branches. A branch more than 15 feet (4.57 m) in length shall be separately vented. The minimum area of any vent installed in a combination waste and vent system shall be one-half the diameter of the drain pipe served, but not less than the minimum indicated in Table 18-29-916.1.

Municipal Code of Chicago § 18-29-912.2.2 Sinks, lavatories, and other fixtures.

18-29-912.2.2 Sinks, lavatories, and other fixtures. Sinks, lavatories and other fixtures that are roughed-in above the floor shall not be permitted on a combination waste and vent.

Municipal Code of Chicago § 18-29-912.3 Size.

18-29-912.3 Size. The minimum size of a combination drain and vent pipe shall be in accordance with Table 18-29-912.3. Table 18-29-912.3 Size of Combination Drain and Vent Pipe (for Floor Drains Only) Diameter Pipe (inches) | Maximum Number of Drainage Fixture Units Connecting to a horizontal branch or stack | Connecting to a building drain or building subdrain Diameter Pipe (inches) | Maximum Number of Drainage Fixture Units Connecting to a horizontal branch or stack | Connecting to a building drain or building subdrain 2 | 3 | 4 2 1/2 | 6 | 26 3 | 12 | 31 4 | 20 | 50 5 | 160 | 250 6 | 360 | 575 For SI: 1 inch = 25.4 mm.

Municipal Code of Chicago § 18-29-913.1 Limitation.

18-29-913.1 Limitation. Island fixture venting shall not be permitted for fixtures other than sinks and lavatories. Residential kitchen sinks with a dishwasher waste connection, a food waste grinder, or both, in combination with the kitchen sink waste, shall be permitted to be vented in accordance with this section.

Municipal Code of Chicago § 18-29-913.2 Vent connection.

18-29-913.2 Vent connection. The island fixture vent shall connect to the fixture drain as required for an individual or common vent. The vent shall rise 6 inches (150 mm) vertically above the flood rim level of the fixture being vented before offsetting horizontally or vertically downward before connecting to the outside vent terminal.

Municipal Code of Chicago § 18-29-913.3 Vent installation below the fixture flood level rim.

18-29-913.3 Vent installation below the fixture flood level rim. The vent located below the flood level rim of the fixture being vented shall be installed as required for drainage piping in accordance with Article 7, except for sizing. The vent shall be sized in accordance with Section 18-29-916.2. The lowest point of the island fixture vent shall connect full size to the drainage system. The connection shall be to a vertical drain pipe or to the top half of a horizontal drain pipe. Clean-outs 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 clean-out.

Municipal Code of Chicago § 18-29-914.1 Where required.

18-29-914.1 Where required. Soil and waste stacks in buildings having more than 10 branch intervals shall be provided with a relief vent at each tenth interval installed, beginning with the top floor.

Municipal Code of Chicago § 18-29-914.2 Size and connection.

18-29-914.2 Size and connection. The size of the relief vent shall be equal to the size of the vent stack to which it connects. The lower end of each relief vent shall connect to the soil or waste stack through a wye below the horizontal branch serving the floor, and the upper end shall connect to the vent stack through a fitting not less than 42 inches (1067 mm) above the floor. (Amend Coun. J. 11-8-12, p. 38872, § 370; Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 5)

Municipal Code of Chicago § 18-29-915.1 Vent for horizontal offset of drainage stack.

18-29-915.1 Vent for horizontal offset of drainage stack. Horizontal offsets of drainage stacks shall be vented where five or more branch intervals are located above the offset. The offset shall be vented by venting the upper section of the drainage stack and the lower section of the drainage stack. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 6)

Municipal Code of Chicago § 18-29-915.2 Upper section.

18-29-915.2 Upper section. The upper section of the drainage stack shall be vented as a separate stack with a vent stack connection installed in accordance with Section 18-29-903.4. The offset shall be considered the base of the stack.

Municipal Code of Chicago § 18-29-915.3 Lower section.

18-29-915.3 Lower section. The lower section of the drainage stack shall be vented by a yoke vent connecting between the offset and the next lower horizontal branch. The yoke vent connection shall be permitted to be a vertical extension of the drainage stack. The size of the yoke vent and connection shall be a minimum of the size required for the vent stack of the drainage stack.

Municipal Code of Chicago § 18-29-916.1 Size of stack vents and vent stacks.

18-29-916.1 Size of stack vents and vent stacks. The minimum required diameter of stack vents and vent stacks shall be determined from the developed length and the total of drainage fixture units connected thereto in accordance with Table 906.1, but in no case shall the diameter be less than one-half the diameter of the drain served, or less than 1 1/4 inches (32 mm). Table 18-29-916.1 Size and Developed Length of Stack Vents and Vent Stacks Diameter of Soil or Waste Stack (inches) | Total Fixture Units Being Vented (dfu) | Maximum Developed Length of Vent (feet) a Diameter of Vent (inches) 1 1/4 b | 1 1/2 b | 2 | 2 1/2 | 3 | 4 | 5 | 6 | 8 | 10 | 12 Diameter of Soil or Waste Stack (inches) | Total Fixture Units Being Vented (dfu) | Maximum Developed Length of Vent (feet) a Diameter of Vent (inches) 1 1/4 b | 1 1/2 b | 2 | 2 1/2 | 3 | 4 | 5 | 6 | 8 | 10 | 12 1 1/4 1 1/2 1 1/2 | 2 8 10 | 30 50 30 | – 150 100 | – | – | – | – | – | – | – | – | – 2 2 2 1/2 | 12 20 42 | – 30 26 | 75 50 30 | 200 150 100 | – – 300 | – | – | – | – | – | – | – 3 3 3 | 10 21 53 | – | 42 32 27 | 150 110 94 | 360 270 230 | 1,040 810 680 | – | – | – | – | – | – 3 4 4 | 102 43 140 | – | 25 – – | 86 35 27 | 210 85 65 | 620 250 200 | – 980 750 | – | – | – | – | – 4 4 5 | 320 540 190 | – | – | 23 21 – | 55 50 28 | 170 150 82 | 640 580 320 | – – 990 | – | – | – | – 5 5 5 | 490 940 1,400 | – | – | – | 21 18 16 | 63 53 49 | 250 210 190 | 760 670 590 | – | – | – | – 6 6 6 | 500 1,100 2,000 | – | – | – | – | 33 26 22 | 130 100 84 | 400 310 260 | 1,000 780 660 | – | – | – 6 8 8 | 2,900 1,800 3,400 | – | – | – | – | 20 – – | 77 31 24 | 240 95 73 | 600 240 190 | – 940 729 | – | – 8 8 10 | 5,600 7,600 4,000 | – | – | – | – | – | 20 18 – | 62 56 31 | 160 140 78 | 610 560 310 | – – 960 | – 10 10 10 | 7,200 11,000 15,000 | – | – | – | – | – | – | 24 20 18 | 60 51 46 | 240 200 180 | 740 630 571 | – 12 12 12 | 7,300 13,000 20,000 | – | – | – | – | – | – | – | 31 24 20 | 120 94 79 | 380 300 250 | 940 720 610 12 15 15 | 26,000 15,000 25,000 | – | – | – | – | – | – | – | 18 – – | 72 40 31 | 230 130 96 | 500 310 240 15 15 | 38,000 50,000 | – | – | – | – | – | – | – | – | 26 24 | 81 74 | 200 180 For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm. a. The developed length shall be measured from the vent connection to the open air. b. Not permitted for water closets. (Amend Coun. J. 3-27-02, p. 82090, § 3; Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)

Municipal Code of Chicago § 18-29-916.2 Vents other than stack vents or vent stacks.

18-29-916.2 Vents other than stack vents or vent stacks. 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 18-29-710B. Vent pipes shall be not less than 1 1/4 inches (32 mm) in diameter. Relief vents for soil and waste stacks in buildings having more than 10 branch intervals shall be sized in accordance with Section 18-29-914.2. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)

Municipal Code of Chicago § 18-29-916.3 Developed length.

18-29-916.3 Developed length. The developed length of individual, branch, circuit and relief vents shall be measured from the farthest point of vent connection to the drainage system to the point of connection to the vent stack, stack vent or termination outside of the building. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)

Municipal Code of Chicago § 18-29-916.4 Multiple branch vents.

18-29-916.4 Multiple branch vents. Where multiple branch vents are connected to a common branch vent, the common branch vent shall be sized in accordance with this section based on the size of the common horizontal drainage branch that is or would be required to serve the total drainage fixture unit load being vented. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)

Municipal Code of Chicago § 18-29-916.5 Sump vents.

18-29-916.5 Sump vents. Sump vent sizes shall be determined in accordance with Sections 18-29-916.5.1 and 18-29-916.5.2. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)

Municipal Code of Chicago § 18-29-916.5.1 Sewage pumps and sewage ejectors other than pneumatic.

18-29-916.5.1 Sewage pumps and sewage ejectors other than pneumatic. Drainage piping below sewer level shall be vented in the same manner as that of a gravity system. Building sump vent sizes for sumps with sewage pumps or sewage ejectors, other than pneumatic, shall be determined in accordance with Table 18-29-916.5.1. Table 18-29-916.5.1 Size and Length of Sump Vents Discharge Capacity of Pump (gpm) | Maximum Developed Length of Vent (feet) a Diameter of vent (inches) 1 1/4 | 1 1/2 | 2 | 2 1/2 | 3 | 4 Discharge Capacity of Pump (gpm) | Maximum Developed Length of Vent (feet) a Diameter of vent (inches) 1 1/4 | 1 1/2 | 2 | 2 1/2 | 3 | 4 10 | No limit b | No limit | No limit | No limit | No limit | No limit 20 | 270 | No limit | No limit | No limit | No limit | No limit 40 | 72 | 160 | No limit | No limit | No limit | No limit 60 | 31 | 75 | 270 | No limit | No limit | No limit 80 | 16 | 41 | 150 | 380 | No limit | No limit 100 | 10 c | 25 | 97 | 250 | No limit | No limit 150 | NP | 10 c | 44 | 110 | 370 | No limit 200 | NP | NP | 20 | 60 | 210 | No limit 250 | NP | NP | 10 | 36 | 132 | No limit 300 | NP | NP | 10 c | 22 | 88 | 380 400 | NP | NP | NP | 10 c | 44 | 210 500 | NP | NP | NP | NP | 24 | 130 For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon per minute = 3.785 L/m. NP = Not permitted. a. Developed length plus an appropriate allowance for entrance losses and friction due to fittings, changes in direction and diameter. Allowances shall be obtained from NBS Monograph 31 or other engineered sources. An allowance of 50 percent of the developed length shall be assumed if a more precise value is not available. b. Actual values greater than 500 feet. c. Less than 10 feet. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)

Municipal Code of Chicago § 18-29-916.5.2 Pneumatic sewage ejectors.

18-29-916.5.2 Pneumatic sewage ejectors. The air pressure relief pipe from a pneumatic sewage ejector shall be connected to an independent vent stack terminating as required for vent extensions through the roof. The relief pipe shall be sized to relieve air pressure inside the ejector to atmospheric pressure but shall be not less than 1 1/2 inches (38 mm) in size. (Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)

Municipal Code of Chicago § 18-29-917.1 Not required.

18-29-917.1 Not required. No vent will be required on a downspout trap, a subsoil catch basin trap draining by gravity to the house drain or sewer, or a basement floor drain which branches into the house drain at a distance of more than 5 feet from any soil or waste stack. Other floor drains below grade shall be vented at the end of the waste line or individually vented.
Source: City of Chicago, Municipal Code of Chicago (American Legal Publishing, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/chicago/latest/chicago_il/0-0-0-2692422Fetched: 10/24/2026

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