Heads up: There are no amended sections in this chapter.
  1. The protection of trap seals from siphonage, aspiration, or backpressure shall be accomplished by the appropriate use of sanitary drain stacks with adequate venting in accordance with the requirements of this Code.
  2. Venting systems shall be designed and installed so that at no time will trap seals be subjected to a pneumatic pressure differential of more than one inch of water column under design load conditions.
  3. If a trap seal is subject to loss by evaporation, means shall be provided to prevent the escape of sewer gas. See Section 5.3.6.
See Figures 12.2.1-A and 12.2.1-B
Figure 12.2.1 - A
TRAP SEAL REDUCTION FROM 1" NEGATIVE PRESSURE
Figure 12.2.1 - B
TRAP SEAL REDUCTION FROM 1" POSITIVE PRESSURE
  1. Where drain stacks have ten or more branch intervals, a relief vent shall be provided for each ten branch intervals, starting at the top of the drain stack.
  2. The lower end of each relief vent shall connect to the drain stack as a yoke vent below its tenth branch interval.
  3. The upper end of the relief vent shall connect to the vent stack for the drain stack at an elevation not less than 3 feet above the floor level served by the branch interval.
  4. Yoke vents shall connect to the drain stack as an upward wye branch and shall be the same size as the vent stack that they are connected to. Yoke vents shall be vertical or no more than 45 degrees from vertical.
See Figure 12.3.2
Comment: Relief vents for vertical drain stacks provide pressure relief ahead of heavy drain flows and vacuum relief behind heavy drain flows.
Figure 12.3.2
RELIEF FOR DRAIN STACKS HAVING 10 OR MORE BRANCH INTERVALS
  1. Stack vents shall extend from the top of a drain stack to an outdoor vent terminal.
  2. A vent stack shall be provided for drain stacks having five or more branch intervals.
  3. Where vent stacks are provided, their lower connection near the base of the drain stack for pressure relief, shall be either:
    1. to the drain stack at or below its lowest branch connection or,
    2. to the building drain within 10 pipe diameters downstream from the base of the drain stack.
  4. The upper connection of vent stacks shall be to the stack vent for the drain stack or to an outdoor vent terminal.
  5. Vent stacks shall be permitted to be provided for drain stacks having less than five branch intervals.
  6. Stack vents and vent stacks shall be sized in accordance with Section 12.16.4.
See Figure 12.3.1
Figure 12.3.1
VENT STACKS FOR DRAIN STACKS HAVING 5 OR MORE BRANCH INTERVALS
  1. Horizontal offsets in stacks having five or more branch intervals discharging above the offset shall be vented either:
    1. by considering the stack as two separate stacks, one above and one below the offset, and venting each separately.
    2. by providing a yoke vent from the drain stack below the offset to the vent stack required by Section 12.3.1 not less than 3 feet above the offset. This relief vent may be a stack vent for the lower portion of the drain stack.
See Figures 12.3.3-A and 12.3.3-B
Figure 12.3.3 - A
ONE STACK VENT FOR HORIZONTAL OFFSETS IN DRAIN STACKS
Figure 12.3.3 - B
TWO VENT STACKS FOR HORIZONTAL OFFSETS IN DRAIN STACKS
Where vertical offsets in drain stacks having five or more branch intervals above the offset have branch connections within 2 feet above or below the offset, a relief vent shall be provided for the lower portion of the stack below the offset.
Vents may be connected into a common header at the top of one or more stacks and then be extended to the open air at one point.
The plumbing vent system shall not be used for purposes other than venting of the plumbing system.
Vent pipes shall terminate not less than 6 inches above the roof, measured from the highest point where the vent intersects the roof.
EXCEPTION: Where a roof is used for any purpose other than weather protection and maintaining equipment, vents within ten (10) feet of the area being utilized shall extend at least seven (7) feet above the roof, shall be properly supported, and shall also comply with Section 12.4.4 for location.
See Figure 12.4.1
Figure 12.4.1
VENT EXTENSIONS THROUGH THE ROOF
Vent terminals shall be made watertight with the roof by proper flashing.
Vent terminals shall not be used for the purpose of flag poling, TV aerials, or similar purposes.
Vent and branch vent pipes shall be free from drops and sags and be sloped and connected so as to drain by gravity to the drainage system. See Figure 12.6.1
Figure 12.6.1
VENT PIPING SLOPE
  1. Vent terminals shall not be located where vapors can enter the building.
  2. No vent terminal shall be located directly beneath any door, window, or other ventilating opening of a building or of another building, nor shall any such vent terminal be within 10 feet horizontally of such opening unless it is at least 2 feet above the top of such opening.
  3. Where a vent terminal is within 10 feet horizontally and less than 2 feet above a ventilation opening described in Section 12.4.4.b and the line-of-sight from the vent terminal to the ventilation opening is interrupted by the continuous ridge of a roof, the ridge shall be at least 2 feet above the top of the opening. Otherwise, the vent terminal shall comply with Section 12.4.4.b.
  4. Where a vent terminal is within 10 feet horizontally and less than 2 feet above a ventilation opening described in Section 12.4.4.b and the line of sight from the vent terminal to such ventilation opening is interrupted by a solid wall or solid barrier, the top of the wall or barrier shall be at least 2 feet above the top of the ventilation opening and the shortest travel distance around the wall or barrier from the vent terminal to the nearest edge of the ventilation opening shall be at least 10 feet. Otherwise, the vent terminal shall comply with Section 12.4.4.b.
See Figure 12.4.4
Figure 12.4.4
ALLOWABLE LOCATIONS FOR VENT TERMINALS
Vent terminals shall be permitted to extend through a wall on an existing building. They shall be at least 10 feet horizontally from any lot line, 10 feet above existing grade, and terminate with a corrosion-resistant bird screen. Vent terminals shall not terminate under an overhang of a building. They shall be located in accordance with Section 12.4.4.
No sanitary drain or vent pipe extension shall be installed on the outside of a wall of any new building, but shall be carried up inside the building
EXCEPTION: In those localities where the outdoor temperature does not drop below 32°F, the Authority Having Jurisdiction may approve the installation outside the building.
  1. Vent terminals through the roof shall be made watertight to the roof by sealing the flashing to either the exterior or interior of the vent terminal.
  2. Vent terminals that are externally sealed shall employ manufactured vent stack flashing sleeves, roof couplings, or no-caulk roof vent flashings.
  3. Where vent terminals are sealed by counter-flashing over the top of the vent terminal, the counter-flashing shall not decrease the interior free area of the minimum required vent terminal size. Vent terminals shall be increased at least one pipe size when counter-flashed. Interior counter-flashing shall be sealed gas-tight to prevent the entrance of sewer gas into the building through the flashing.
Vent terminals shall not be covered by hoods, caps, or other devices that restrict air flow into and out of the vent terminal.
Such devices shall have unrestricted open areas not less than the cross-sectional area of the vent pipe they are connected to.
Every vent shall rise vertically to a minimum of 6 inches above the flood level of the rim of the fixture being served.
EXCEPTIONS:
  1. Horizontal portions of a vent below the flood level rim of the fixture served that are installed in accordance with Sections 12.6.2.1, 12.6.2.2, and 12.6.2.3.
  2. Island sink vents in accordance with Section 12.18.
See Figures 12.6.2-A and 12.6.2-B
Figure 12.6.2 - A
VENT PIPE CONNECTIONS TO HORIZONTAL DRAINS
Figure 12.6.2 - B
HORIZONTAL VENT PIPING BELOW THE FLOOD LEVEL RIM OF FIXTURES
Where a vent pipe connects to a horizontal fixture drain branch, and conditions require a horizontal offset in the vent below the flood level rim of the fixture served, the vent shall be taken off so that the invert of the horizontal portion of the vent pipe is at or above the centerline of the horizontal sanitary drain pipe.
The portion of the horizontal vent installed below the flood level rim, as permitted in Section 12.6.2.1, shall be installed with the slope required to drain by gravity to the drainage system. See Figure 12.6.2-B
Cleanouts shall be provided in the vent piping so that any blockages in the vent piping below the flood level rim of the fixture served can be cleared into the drainage system.
Connections between any horizontal vent pipe, including individual vents, branch vents, relief vents, circuit vents or loop vents, and a vent stack or stack vent shall be made at least 6 inches above the flood level rim of the highest fixture on the floor level.
  1. Side-inlet closet bends shall be permitted only in cases where the fixture connection thereto is vented.
  2. In no case shall the side-inlet be used to vent a bathroom group without being washed by a fixture.
EXCEPTION: As allowed in Section 12.10.
Two fixtures set adjacent within the distance allowed between a trap and its vent, may be served with one common vent, provided that each fixture connects separately into an approved double fitting having inlet openings at the same level.
See Section 12.9.2 for inlet openings at different levels.
See Figure 12.7
Comment: Suitable double fittings for connecting adjacent fixtures such as lavatories, sinks, tubs, showers, urinals, or floor-outlet water closets to a stack are double sanitary tees, double fixture fittings (plastic), and sanitary crosses. These fittings have high branch openings into the stack that keep the top of the vent opening above the weir of the traps to prevent self-siphonage.
Figure 12.7
VENTING ADJACENT FIXTURES CONNECTED TO A VERTICAL DRAIN AT THE SAME LEVEL
Fixture drains shall have a vent so located that the vent connects above the top weir of the trap and the developed length of the trap arm is within the limits set forth in Table 12.8.1.
EXCEPTIONS:
  1. Water closets and similar siphonic fixtures.
  2. Combination waste and vent systems. See Section 12.17
  3. Vents may be connected below the top weir of the fixture trap if the following conditions are met:
    1. The vertical section of the drain pipe shall be at least one pipe size larger than the trap inlet size.
    2. The horizontal pipe connected to the trap outlet shall be at least two pipe diameters long.
    3. The developed length of the trap arm shall not exceed the values in Table 12.8.1.
Table 12.8.1
MAXIMUM LENGTH OF TRAP ARMS
Size of Trap Arm (Inches) Length — Trap Arm to Vent Slope — Inches per Foot
1-1/4 3' 6" 1/4
1-1/2 5' 1/4
2 8' 1/4
3 10' 1/8
4 12' 1/8
NOTES FOR TABLE 12.8.1:
This table has been expanded in the "length" requirements to reflect expanded application of the wet venting principles. Slope shall not exceed 1/4" per foot.
Figure 12.8.1-A
THE MAXIMUM LENGTH OF TRAP ARMS
Figure 12.8.1 - B
EXAMPLES OF EXCEPTION (3) TO SECTION 12.8.1 (VENT CONNECTIONS BELOW THE WEIR OF A TRAP)
A vent shall not be installed within two pipe diameters of the trap weir. See Figure 12.8.3
Figure 12.8.3
CROWN VENTS ARE PROHIBITED
For water closets, clinical sinks, and flushing-rim service sinks with integral traps, the distance between the outlet of the fixture and its vent connection shall not exceed three (3) feet vertically and nine (9) feet horizontally.
An individual vent, installed vertically, may be used as a common vent for two fixture traps when both fixture drains connect with a vertical drain at the same level.
A common vent may be used for two fixtures installed on the same floor but connecting to a vertical drain at different levels, provided that the vertical drain is one pipe size larger than the upper fixture drain but in no case smaller than the lower fixture drain. See Figure 12.9.2
Figure 12.9.2
COMMON VENTING FIXTURES CONNECTED TO A VERTICAL DRAIN AT DIFFERENT LEVELS
  1. Wet vent piping shall be sized to drain the fixtures upstream and vent the fixtures downstream.
  2. Each section of wet vent piping shall be: (1) not less than one pipe size larger than the minimum required drain pipe for the upstream fixtures that they drain, and (2) not less than one pipe size larger than the minimum required vent pipe for the downstream fixtures being wet vented by that section, whichever is larger.
  3. Dry vents shall be not less than one-half the minimum required pipe size for the drain piping that serves all of the fixtures being wet vented and dry vented.
Comment: Wet vents must be not less than one pipe size oversize for draining the upstream fixtures and not less than one pipe size oversize for venting the downstream fixtures.
  1. An individual water closet may be wet vented by an adjacent lavatory.
  2. The wet vent from the lavatory drain shall be not less than one pipe size larger than one-half the size of the drain from the water closet.
  3. The maximum length of the water closet trap arm to its wet vent connection shall comply with Section 12.8.4, horizontally and vertically.
  4. The dry vent from the wet vent at the lavatory connection shall be not less than one-half the size of the drain from the two fixtures.
See Figures 12.10.2 and 1.2.77
  1. Water closets and bathtubs or shower stalls in bathroom groups may be wet vented by the lavatories.
  2. The dry vent pipe from the lavatories shall be not less than one-half the size of the drain pipe for the group.
  3. The size of wet vent piping shall comply with the following: (1) be not less than one pipe size larger than the required drain pipe size for its upstream fixtures, and (2) be not less than one pipe size larger than one-half the size of the largest connected drain piping being wet vented downstream.
  4. The connection of fixture drains to horizontal wet vents shall be horizontal. Except for water closets, the upper portion of the wet vent opening shall not be below the weir of the fixture trap.
  5. The bathtubs or shower stalls may be connected to their water closet drain upstream from its wet vent connection.
  6. The maximum length of the fixture trap arms for lavatories, bathtubs, and shower stalls shall comply with Section 12.8.1.
  7. The maximum length of the water closet trap arms to their wet vent connection shall comply with Section 12.8.4, horizontally and vertically.
  8. Where fixtures are wet vented vertically, water closets shall connect to the wet vent at the same lowest elevation. Bathtubs or shower stalls shall connect to the wet vent at the same elevation as the water closets or higher.
Refer to Figures 12.10.3-A through F
  1. A floor drain or floor sink may be wet vented by an adjacent lavatory or sink.
  2. The size of the drain for the fixtures shall be based on the total drainage fixture units (DFU) connected
  3. The size of the dry vent for the fixtures shall be not less than one-half the pipe size of the drain for both fixtures.
  4. The size of the wet vent between the lavatory or sinks and the floor drain or floor sink shall be: (1) not less than one pipe size larger than the required drain pipe size for the lavatory or sink, and (2) not less than one pipe-size larger than one-half of the drain pipe for both fixtures, whichever is larger.
  5. The maximum lengths of the fixture trap arms shall comply with Section 12.8.1.
  1. A maximum of eight floor-outlet water closets, showers, bathtubs, or floor drains connected in battery on a horizontal drain shall be permitted to be battery-vented.
    EXCEPTION: Blowout type water closets.
  2. Each fixture drain shall connect horizontally to the horizontal drain being so vented.
  3. The horizontal battery-vented drain shall be considered as a vent extending from the most downstream fixture drain connection to the most upstream fixture drain connection.
  4. Back-outlet water closets and wall-mounted urinals shall be permitted to be battery-vented provided that no floor-outlet fixtures are connected to the same horizontal battery-vented drain.
    EXCEPTION: Back-outlet blowout type water closets.
  5. The battery vent shall be a circuit or loop vent connected to the horizontal drain between the two most upstream fixture drains and shall be installed in accordance with Section 12.6.
  6. The entire length of the vented section of the horizontal battery-vented drain shall be uniformly sized for the total drainage fixture units (DFU) connected thereto.
  7. The maximum slope of the horizontal battery-vented drain shall be 1 inch per foot.
  8. A relief vent shall be provided on battery-vented horizontal drains that have four or more water closets connected on the lower floors of a drain stack or connect to the building drain or a branch of the building drain.
  9. The relief vent shall connect to the horizontal battery-vented drain between its most downstream fixture drain connection and its connection to a drain stack, the building drain, or branch of the building drain.
  10. Relief vents shall be installed in accordance with Section 12.6.
  11. Circuit, loop, and relief vents shall be permitted to connect to a fixture drain, common vent, or continuous vent for fixtures located within the same branch interval as the battery-vented horizontal drain.
    EXCEPTION: Fixture vents for more than four drainage fixture units (DFU) shall not connect to a battery vent.
  12. Lavatories and similar fixtures shall be permitted to connect to the horizontal battery-vented drain, either horizontally or vertically, provided that, (1) the fixtures are on the same floor as the battery-vented drain, and (2) the fixtures have individual, common, or continuous vents.
  13. Batteries of more than eight battery-vented fixtures shall have a circuit or loop vent for each group of eight or less fixtures.
  14. Where there are two or more groups of battery-vented fixtures, the horizontal drain for each downstream group shall be sized for the total drainage fixture units (DFU) into that group, including any upstream groups and the fixtures within the group being sized.
  15. Horizontal battery-vented drains that connect to drain stacks shall be sized as horizontal fixture branches in accordance with Table 11.5.1B.
  16. Horizontal battery-vented drains that connect to the building drain or a branch of the building drain shall be sized as a branch of the building drain in accordance with Table 11.5.1A.
See Figure 12.13.1 and the definitions of "Battery of Fixtures", "Vent, Circuit", and "Vent, Loop".
Figure 12.13.1
CIRCUIT AND LOOP VENTING BATTERIES OF FIXTURES
Where parallel branches of up to eight battery-vented fixtures each are joined prior to connecting to a stack or building drain, the common downstream piping shall be sized for the combined total fixture unit (DFU) load of both branches. A relief vent shall be provided on the common downstream piping when the parallel branches serve a combined total of four or more water closets and connect to a stack receiving drainage from an upper floor.
Circuit, loop, and relief vent connections to horizontal battery-vented drains shall be taken off at a vertical angle or from the top of the horizontal drain. See Figure 12.16.2
When fixtures are connected to one horizontal battery-vented drain through a double wye or a sanitary tee in a vertical position, a common vent for each two fixtures back-to-back or double connected shall be provided. The common vent shall be installed in a vertical position as a continuation of the double drain connection.
Fixtures and gravity drain piping in a building subdrain system shall be vented in the same manner as a conventional gravity drainage system and shall be permitted to connect to vent piping for fixtures and gravity drain piping that are not part of the subdrain system.
  1. The vent pipe for an atmospheric subdrain sump pit shall be sized based on the discharge capacity of its sewage pump or ejector and the drainage load (DFU) connected to the pit, whichever is larger.
    1. The required vent pipe size and length based on the sewage pump or ejector capacity (GPM) shall be determined from Table 12.14.2.
    2. The required vent pipe size and length based on the connected drainage load (DFU) shall be determined from Table 12.16.4.
  2. The atmospheric vent pipe from a sump pit shall be permitted to be connected to gravity vent piping. The sump pit vent shall carry the DFU load on the pit if it is connected to other vent piping and combined with their DFU loads.
    Table 12.14.2
    SIZE AND LENGTH1 OF SUMP VENTS
    Discharge Capacity of Sump Pump (gpm) Diameter of Vent (inches)
    1-1/4 1-1/2 2 2-1/2 3 4
    10 NL2 NL2 NL2 NL2 NL2 NL2
    20 270 NL2 NL2 NL2 NL2 NL2
    40 72 160 NL2 NL2 NL2 NL2
    60 31 75 270 NL2 NL2 NL2
    80 16 41 150 380 NL2 NL2
    100 <103 25 97 250 NL2 NL2
    150 NP4 <103 44 110 370 NL2
    200 NP4 NP4 20 60 210 NL2
    250 NP4 NP4 10 36 132 NL2
    300 NP4 NP4 <103 22 88 380
    400 NP4 NP4 NP4 <103 44 210
    500 NP4 NP4 NP4 NP4 24 130
    NOTES FOR TABLE 12.14.2.
    1. The maximum lengths in the table are the developed lengths of the vent pipes in feet. An allowance has been made for entrance losses and friction for the pipe and fittings.
    2. No Limit; actual values greater than 500 feet.
    3. Less than 10 feet.
    4. Not Permitted.
  1. When a pneumatic sewage ejector requires a surge tank in Section 11.7.4, the tank shall be vented the same as an atmospheric sump pit The vent shall be sized based on its connected DFU load.
  2. Pressure release vents for pneumatic sewage ejectors shall extend to an outdoor vent terminal that is separate from any gravity system vents. Such pressure release vents shall be of sufficient size to reduce the ejector tank to atmospheric pressure within 10 seconds after discharge, but not less than 1-1/4" pipe size.
Where fixture or branch drains connect to a sanitary drain stack within a suds pressure zone as described in Section 11.11.2, a suds relief vent shall be provided for the fixture or branch drain. Suds relief vents shall be 2" minimum size but not less than one pipe size smaller than the drain branch that they serve. Such relief vents shall connect to the drain branch between the suds pressure zone and the first fixture trap on the branch.
Comment: Suds pressure relief vents in Section 12.15.1 are larger than ordinary vents for drainage systems because the suds are heavier than air. Suds can weigh from 2 to as much as 19 pounds per cubic foot.
Table 12.15.1
SUDS PRESSURE RELIEF VENTS
Drain Size (inches) Relief Vent Size (inches)
1-1/2 2
2 2
3 2
4 3
5 4
6 5
8 6
Connections shall not be made within the suds pressure zone of a vent stack that connects at or downstream from the base of a sanitary drain stack, as described in Section 11.11.2.d.
Vents for individual fixtures shall be not less than 1-1/4" size nor less than one-half the size of the fixture drain that they serve. See Figure 12.16.1
Figure 12.16.1
THE SIZE OF INDIVIDUAL FIXTURE VENTS
Circuit or loop vents shall be not less than one-half the size of the horizontal drain that they serve. See Figure 12.16.2
Figure 12.16.2
THE SIZE OF CIRCUIT AND LOOP VENTS
  1. The size of relief vents for circuit or loop vented branches of the drainage system shall be not less than one-half the size of the horizontal battery-vented drain being served.
  2. Relief vents for drain stacks having ten or more branch intervals shall be the same size as the vent stack to which they connect.
  1. Stack vents shall be not less than the pipe size of the top of the drain stack that they are connected to.
  2. Vent stacks, where required, shall be sized in accordance with Table 12.16.4, based on the total drainage fixture unit load (DFU) at the base of the drain stack that they serve. Connections of branch vents to the vent stack from fixtures on floor levels above the base of the drain stack shall not affect the size of the vent stack.
  3. For the purpose of sizing vent stacks, the length of a vent stack in Table 12.16.4 shall be its developed length from its pressure relief connection near the base of the drain stack being vented to its connection to the stack vent at the top of the drain stack. If not connected to the stack vent, the vent stack shall extend to an outdoor vent terminal.
COMMENT: Where a vent stack is required for a drain stack, the drain stack and its stack vent must be the full size of the drain stack at its base as required by Section 11.5.2.2.
Table 12.16.4
SIZE AND LENGTH OF VENT STACKS
Size of Drain Stack (inches) Drainage Fixture Units (DFU) Connected Maximum Developed Length of Pipe (feet) for Vent Stack Size
1-1/4" 1-1/2" 2" 3" 4" 5" 6" 8" 10" 12" 15"
2" 6 129 314 1324
2" 12 90 217 890
2" 18 75 188 739
2" 24 68 168 667
3" 10 61 252 1830
3" 25 35 141 1021
3" 50 25 99 716
3" 72 22 86 625
4" 50 71 533 2101
4" 200 30 220 931
4" 350 23 169 704
4" 500 20 149 616
5" 350 81 330 993
5" 600 61 249 747
5" 850 52 215 642
5" 1,100 48 197 595
6" 700 29 119 361 881
6" 1,100 23 95 286 701
6" 1,500 20 83 250 618
6" 1,900 19 77 231 572
8" 1,500 21 76 187 775
8" 2,200 18 63 155 641
8" 2,900 16 56 138 571
8" 3,600 15 52 129 534
10" 2,600 23 56 232 701
10" 3,600 20 48 199 600
10" 4,600 18 43 180 543
10" 5,600 17 41 169 509
12" 5,400 19 77 235 571
12" 6,400 17 72 219 535
12" 7,400 16 68 208 507
12" 8,400 16 66 200 487
15" 7,000 26 79 193 583
15" 9,000 23 71 173 528
15" 11,000 22 65 160 494
15" 13,000 20 62 152 455
NOTES FOR TABLE 12.16.4:
  1. The maximum developed lengths of pipe in the table are based on a 1" wg pressure drop for a single vent stack from its connection at the base of its drain stack to its connection to its stack vent or to its outdoor vent terminal.
  2. The maximum developed length of pipe is the total length of the pipe alone. The pipe lengths in the table include an allowance for pipe fittings. The total equivalent length of pipe used in the calculations for 1" wg pressure drop is 2/3 pipe and 1/3 fittings.
  1. Vent headers and portions thereof shall be sized according to Table 12.16.6.
  2. The number of drainage fixture units (DFU) used to size sections of vent headers shall be the sum of all fixture units (DFU) for all drain stacks served by that section of the header.
  3. The total developed length of all sections of a vent header shall be the longest vent length from the vent stack connection at the base of the most distant drain stack to the outdoor vent terminal.
  4. Where two or more vent headers are connected before reaching an outdoor vent terminal, each vent header shall have its own total developed length to the outdoor vent terminal with regard to sizing per Table 12.16.6.
  1. Branch vents and portions thereof shall be sized according to Table 12.16.6.
  2. The number of drainage fixture units (DFU) used to size sections of branch vents shall be the sum of all drainage fixture units (DFU) for the individual fixture vents or branch vents served by that section of the branch vent.
  3. The total developed length of all sections of a branch vent shall be the longest length from its connection to the most distant individual fixture vent being vented to its connection to an outdoor vent terminal.
    Table 12.16.6
    SIZE OF BRANCH VENTS (1)
    AND VENT HEADERS (2)
    DFU Being Vented Vent Pipe Size (minimum) For 40 Feet Maximum Total Developed Length Vent Pipe Size (minimum) For Greater than 40 Feet Total Developed Length
    1 1-1/4" 1-1/2"
    3 1-1/4" 1-1/2"
    6 1-1/4" 1-1/2"
    20 1-1/2" 2"
    160 2" 3"
    360 3" 4"
    620 3" 4"
    1400 4" 5"
    2500 5" 6"
    3900 6" 8"
    7000 8" 10"
    NOTES FOR TABLE 12.16.6:
    1. The total developed length of branch vents shall comply with Section 12.16.6.c.
    2. The total developed length of vent headers shall comply with Section 12.16.5.c or d
The minimum size of vent piping installed underground shall be 1-1/2".
  1. Each building drain shall be vented by the vent terminals of its connected drain piping.
  2. The aggregate internal cross-sectional area of all vent terminals serving a building drain shall be not less than the cross-sectional area of the minimum required size of the building drain that they serve, at the point where it connects to the building sewer. Table 12.16.8 shall be used for the cross-sectional areas of nominal pipe sizes.
    EXCEPTION: The aggregate cross-sectional area requirement shall be exclusive of any requirements to increase the size of a vent terminal to prevent frost closure under Section 12.5.
  3. One or more vent terminals having the aggregate internal cross-sectional area of a 3" vent terminal shall be permitted to vent a 4" building drain if the drainage fixture unit load (DFU) and number of bathroom groups served by the building drain does not exceed the maximum number allowed on a 3" building drain, as permitted by Section 11.5.6.c.
Table 12.16.8
NOMINAL PIPE CROSS SECTIONAL AREA (Sq. Inches)
Nominal Pipe Size (ID) Cross Sectional Area (sq in.)
1-1/4" 1.2
1-1/2" 1.8
2" 3.1
2-1/2" 4.9
3" 7.1
4" 12.6
5" 19.6
6" 28.3
8" 50.3
10" 78.5
12" 113.1
15" 176.7
  1. A combination waste and vent system shall be permitted only where conditions preclude the installation of a conventionally vented drainage system as otherwise required by this Code.
  2. Combination waste and vent systems shall be limited to floor drains and other floor receptors, sinks, lavatories, and standpipes.
Traps in a combination waste and vent system shall be the normal size for the particular fixture. See Table 5.2
  1. Fixtures shall be considered to be vented at the point that they connect to a combination waste and vent system.
  2. Where fixtures have conventionally sized trap arms, the maximum length of the trap arm from the weir of its trap to the point of connection to the combination waste and vent systems shall be as limited in Table 12.8.1.
  3. In the case of fixtures with above-the-floor outlets, the vertical drop at the end of the trap arm shall be one size larger than the trap arm and be considered as the beginning of the combination waste and vent system.
  4. Floor-outlet fixtures shall also be permitted to drop into a vertical combination waste and vent that is at least one size larger than the trap arm.
  5. Where a fixture trap arm is sized as a combination waste and vent, its length shall not be limited and it shall be considered as a branch of the combination waste and vent system.
  6. The maximum vertical drop from a fixture trap arm to a horizontal drain below shall be 6 feet.
The piping in a combination waste and vent system shall be sized according to Table 12.17.4, based on the number of drainage fixture units (DFU) served and the slope of the piping.
EXCEPTION: No pipe shall be smaller than any section of piping upstream, including vertical drops from trap arms.
Table 12.17.4
PIPE SIZING FOR COMBINATION WASTE AND VENT SYSTEMS
Load slope 1/8" per ft slope 1/4" per ft slope 3/8" per ft slope 1/2" per ft
3 dfu 4" 2" 2" 2"
12 dfu 4" 4" 3" 3"
20 dfu 5" 4" 4" 4"
180 dfu 5" 5" 4" 4"
218 dfu 6" 5" 5" 5"
390 dfu 8" 8" 5" 5"
480 dfu 8" 8" 6" 6"
700 dfu 8" 8" 6" 6"
840 dfu 10" 8" 8" 8"
1600 dfu 10" 10" 8" 8"
1920 dfu 12" 10" 10" 10"
All piping in a combination waste and vent system shall be horizontal and sloped at not greater than 1/2 inch per foot.
EXCEPTIONS:
  1. Vertical drops at the end of trap arms.
  2. Vertical drops of not greater than 45 degrees from horizontal where the vertical drop is not greater than 6 feet and the offset is at least 10 pipe diameters from any turn or branch connection.
  1. Connections to mains and branches within combination waste and vent systems shall be made horizontally at a slope not greater than 1/2 inch per foot.
  2. Branch connections shall not be made in vertical drops or offsets.
The distance between turns, offsets, and branch connections in combination waste and vent piping shall be not less than 10 pipe diameters.
  1. Combination waste and vent systems shall extend to the point of connection to a conventionally sized and conventionally vented drainage system.
  2. At the point of connection, the pipe size of the conventional system shall be at least as large as the combination system, and sized to accept the added drainage load from the combination system.
  3. Such connection from the combination system to the conventional system shall be made at an angle above horizontal of not less than 22-1/2 degrees nor more than 45 degrees.
Where drains from individual fixtures are designed as a combination waste and vent and are connected to a conventional drainage system, the connection from the fixture to the conventional system shall be made according to Section 12.17.8.
Island sink venting shall be permitted for sinks and lavatories where the vent pipe cannot rise 6 inches above the flood level rim of the fixture before turning horizontal. Kitchen sinks in dwelling units with dishwasher connections, food waste disposer connections, or both, shall be permitted to be island vented. See Figure 12.18
The island vent pipe shall rise vertically under the sink at the end of the fixture trap arm up to the underside of the counter top for the sink. The vent shall then turn downward and connect to the horizontal drain line below the floor downstream from the fixture drain connection so that the vertical vent drop will drain by gravity to the drainage system. A horizontal vent pipe shall be extended under the floor from the vertical vent drop to a point where it can rise vertically. The vertical rise at the end of the horizontal vent portion shall extend upward to at least 6 inches above the flood level rim of the fixture being vented before turning horizontal and connecting to a vent to the outdoors. The horizontal portion of the vent under the floor shall pitch back toward the sink so that it will drain by gravity through the vertical vent drop connection to the drainage system. See Figure 12.18
Island vent pipes shall be sized as individual or common vents in accordance with Section 12.16.1.
Cleanouts shall be provided in the vertical vent drop under the sink and in the vertical rise beyond the horizontal portion of the vent so that any blockages in the vent piping can be rodded into the drainage system.
Figure 12.18
ISLAND SINK VENTING
Lavatories, bathtubs, showers, kitchen sinks with and without food waste disposers and dishwashers, laundry sinks, clothes washer standpipes, drinking fountains, floor drains, and similar fixtures shall be permitted to be vented by a waste stack that is sized and installed in accordance with the requirements of this Section.
Water closets and urinals shall not be vented by waste stacks.
  1. Waste stacks shall be uniformly sized from bottom to top according to the total connected drainage fixture unit (DFU) load at its base in accordance with Table 12.9.5. The maximum allowable DFU in one branch interval shall be as indicated.
  2. Waste stacks shall be vertical for their entire height without offsets of any degree, except for the base of the stack below the lowest fixture connection.
  1. Each fixture shall individually connect to the vented waste stack through a single or double sanitary tee.
  2. The maximum length of the trap arms from the individual fixtures shall be in accordance with Table 12.8.1.
Waste stack sizes shall be in accordance with Table 12.19.5.
Table 12.19.5
WASTE STACK SIZES FOR WASTE STACK VENTING
Stack Size (inches) Total DFU into One Branch Interval Total DFU into the Stack
1-1/2 1 2
2 2 4
3 6 24
4 6 50
5 6 75
6 6 100
  1. Each waste stack shall be vented by a stack vent that is the same size as the waste stack.
  2. Offsets shall be permitted in stack vents for waste stacks above the connection of the top-most fixture on the stack.
See Figure 12.19.6
Figure 12.19.6
WASTE STACK VENTING
Venting systems not described in this Code may be permitted by the Authority Having Jurisdiction if they provide the protection required by Section 12.2.1 and are individually designed by a licensed professional engineer. See Appendix E - SPECIAL DESIGN PLUMBING SYSTEMS.
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