Answers and Analysis

Your procedure meets current UPC requirements. Although many plumbing codes still do, the UPC has not required a “main” vent stack since 1959 when an amendment accepting an equivalent aggregate area of
smaller vents was adopted. Section 904.0, therefore, relates total available vent area to the cross-sectional
area of the largest required building sewer.

Yes, the above scenario meets the requirements of Section 904.1, provided the common building sewer serves the drainage piping of the buildings which are on the same lot and under the same ownership.
There is no limitation to the distance between buildings as long as the aggregate cross-sectional area
of all vents is not less than that of the required common building sewer.

The drawing does not comply with the word or intent of Section 904.0. UPC venting requirements are intended to do two things: (1) to provide venting for all plumbing fixture traps; and (2), to provide air circulation
throughout all parts of the drainage system. To accomplish the latter, aggregate vent area equal to
the largest required building sewer must extend from the sewer through the roof. In the example, this does
not happen.
(See drawing on the following page.)

Yes, the installation of a backwater valve partially obstructs or diminishes the aggregate cross-sectional area of the piping between the sewer and the upper terminal of the vents.
The sewer venting required by Section 904.1 must be achieved through connection to that portion of
the drainage system which is independent of the backwater valve protected segment. This same rationale
applies when venting the sewer through a system which is equipped with a sump pump.

No. The minimum size of the building sewer is determined using Table 7-5 (2003/2006/2009) Table 703.2 (2012) of the plumbing code. Some sewers are governed by other authorities, and sewer sizes are often larger than what the plumbing code requires. Section 904.1 states that “the size of vent piping shall be determined from its length and the total number of fixture units connected thereto, as set forth in the
Table and that the drainage piping of each building and each connection to a public sewer or a private sewage disposal system shall be vented by means of one (1) or more vent pipes, the aggregate cross-sectional area of which shall be not less than that of the largest required building sewer, as determined by the Table .”

The note at the bottom of Table 7-5 (2003/2006/2009) Table 703.2 (2012) limits horizontal vent sections to 1⁄3 of the total length permitted by the Table . This limitation may be waived, provided that vent pipe is increased one pipe size or more for its entire length. For this example, a 21⁄2 inch vent would be required.

No. The submitted sketch does not comply with Section 905.0 (2003/2006/2009/2012), since the vent is taken off the horizontal drainage pipe upstream of the trap being served. Also, each vent pipe must have its invert
taken off above the center line of the horizontal drainage pipe.
Horizontal venting is not acceptable less than 6 inches above the flood level of the fixture served
unless prohibited by structural conditions.

Drainage fittings are required in vents when the venting is installed less than 6 inches above the flood rim of the fixture served, as stated in Section 905.3, because vents installed below the flood level rim of a
fixture are subject to flooding if a stoppage occurs in the drain. This flooded condition will flow from the vent
when the stoppage is cleared, provided that the vent is installed with drainage fittings. If the waste water
does not drain from the vent, the vent is not likely to remain open or clear, which could cause siphonage
of the trap and sewer gas to enter the building.
Vents installed above the flood level rim of a fixture are not subject to flooding caused by stoppages,
because the waste overflows at the fixture when a stoppage in the drain occurs.

The correct fitting to be used for this type of installation is a combination wye and 1⁄8 bend. Section 905.3 states that vents less than 6 inches above the flood level rim of the fixture shall be installed with approved
drainage fittings and material. A sanitary tee installed in a horizontal position is not an approved drainage
fitting.

Yes. Section 905.3 requires that approved drainage fittings be used for vents less than 6 inches above the flood level rim of the fixture. A sanitary tee installed in a horizontal position is not an appropriate drainage
fitting.

Section 706.4 (2003/2006/2009/2012) relates to drainage systems only and has nothing to do with venting. Section 905.3 addresses horizontal venting. This section requires that, unless prohibited by structural
conditions, each vent must rise vertically to a point not less than 6 inches above the flood level rim of the
fixture served, before offsetting horizontally. Then, if structural conditions do exist, such as a window, a
horizontal vent would be acceptable, provided that the horizontal portion of the vent which is less than 6
inches above the flood level rim of the fixture is installed with approved drainage material. Any angle less
than 45 degrees from the horizontal is considered horizontal by definition.

1. The intent of the phrase unless prohibited by structural conditions is not to prevent digging, drilling, sleeving, or chipping, but may be used where the depth of the sewer or the design of the building
provides no other way and where the installation of the horizontal vent 6 inches above the flood rim of
the fixture would weaken the structure, such as by the excessive cutting or notching of the required
beam. Structural conditions include walls or the practical points of vent rise located at greater distances
from traps than the trap arm length as permitted by Table 10-1 (2003/2006/2009) Table 1002.2 (2012); space limitations between ceilings and floors; interference with beams or girders and lack of initial available drain depth.
2. Yes.
3. Yes.
4. No, however, vents less than 6 inches above the flood level rim of the fixture must be installed with
approved drainage fittings, materials, and grade to the drain.

No. There are two reasons why the submitted examples do not comply with the code and are not acceptable. The closet bend as shown would be required to be 45 degree fittings or equal (Section 706.4,
2003/2006/2009/2012) and the horizontal vent less than 6 inches above the flood rim of the fixture is only
permitted when required by structural conditions (Section 905.3), which the drawing does not show.
The intent of the phrase unless prohibited by structural conditions is not to be used to prevent digging,
drilling, sleeving, or chipping, but may be used where the depth of the sewer or the design of the building
provides no other way and where the installation of the horizontal vent six inches above the flood rim of
the fixture would weaken the structure such as the excessive cutting or notching of a required beam. The
"UPC Illustrated Training Manual" shows acceptable methods of venting a water closet.

No, unless prohibited by structural conditions, a common vent that serves two or more fixtures must rise vertically to a point not less than 6 inches above the flood level rim of the highest fixture served, before
offsetting horizontally.

When unavoidable structural conditions prohibit vertical rise (minimum 6 inches above the flood level rim of the fixture), the first alternative would be a longer trap arm. Should the conditions prohibit this, the horizontal portion of the vent must be raised as high as possible, graded back to the drain, and utilize drainage fittings for all portions of the vent.

Yes. Section 905.3 requires vents to rise vertically and makes allowances for running the vent below the flood rim of the fixture using drainage fittings. Island venting (Section 909.0) is specifically designed for
sinks and similar equipment, mounted in an island, which is a fixture not connected to an adjoining wall
that would allow the installation of a conventional waste and vent system. Inconvenience is not a reason
to allow this type of installation.
See also 909.0

Yes. Section 905.2 of the UPC states that “where vents connect to a horizontal drainage pipe, each vent pipe shall have its invert taken off above the drainage centerline of such pipe downstream of the trap being served”. Additionally, vents that offset horizontally below the flood-level-rim of the fixture being served shall be installed with approved drainage fittings, material and grade to the drain.

The word undiminished is intended to prevent reduction of the required cross-sectional area of any section of a vent or vent piping system between its point of origin and its terminus.
The intent of this section is to assure that individual or combined vent pipe systems have the individual
or aggregate area needed to prevent pressure migrations within the waste vent system in excess of a one
inch water column.
(See the drawing on the following page.)

No. Except for water closets and similar fixtures, a double wye is not acceptable as a double fixture fitting for back-to-back or side-by-side installations. Listed double fittings for such installations are designed so
the vent opening is above the weir of the trap to prevent trap siphonage and sewer gas from entering the
room or building.

No. Any vent that does not terminate vertically 6 inches or more above the roof, as required in Section 906.1, is not acceptable. The open sides or ends in the building as described do not have any effect on
waiving termination requirements. Sewer gas is too dangerous and unsanitary to allow in any part of a
building or structure.

There is no doubt that the pipe is exposed to sharp surfaces where it passes through the flashing. However, because of the function and configuration of the flashing, it is doubtful that the exposure to its
sharp surfaces could result in perceptible damage during installation, or as a consequence of long term
service.
Additional protection for the ABS pipe is not required where it passes through a metal flashing.
see also 313.5 (2003/2006), 313.4 (2009) 312.4 (2012) and IS 5

Any sanitary vent that terminates less than 10 feet from or 3 feet above any opening into the building where sewer gas could enter the building is a violation of the Code. The word opening does include such openings
as eaves, gables, and dormer vents in attic and joist areas. The committee is aware that the building
code does not require an access opening from the habitable area under certain conditions, but the potential
of dangerous and hazardous sewer gas entering any part of the building is not acceptable.

Flagpoling, as used in Section 906.3, is a term defining any vent that exceeds the minimum vertical distance required above the roof and requires additional support such as guy wires, brackets, or other
means of restraining movement.
The local Authority Having Jurisdiction is required to determine if a vent is flagpoled, since several
factors have to be considered, such as, type of material, pipe size, and location of joints below the roof.

Flagpoling was defined in the 2006 Illustrated Training Manual (ITM) as “any vertical vent pipe that has more of its total length above the roof penetration (fulcrum) than below it shall be defined as ‘flagpoled’. This mechanical advantage may result in wind or physical contact causing displacement of the piping both above and below the roof penetration.” Sometimes because of structural conditions a vent may have to be extended to a point of termination above an air intake into a building or above a window or door as required by section 906.2. In such cases the vent would be required to be secured in such a way as to prevent it from swaying in windy conditions which could eventually cause the vent pipe to fail and break off at surface of the roof.

Section 908.1 requires wet venting to be limited to vertical drainage piping receiving the discharge from
trap arms only. The term continuous vent applies to the vent above the top fixture only of an assembly of
wet vented fixtures.
Therefore, your proposed drawings do not comply with the vertical wet venting requirements of Section
908.1.

No. Wet venting is limited to vertical drainage piping receiving the discharge from the trap arm of one and
two fixture unit fixtures.

Yes, provided that the branch serving more than one trap on a combination waste and vent systems does not exceed 15 feet in length and has a cleanout installed at its upper terminal, as required by Section 910.6.
See also Appendix B

Section 908.4 (2006)908.2 (2009/2012) code does not address a length maximum for the horizontal wet vent. The length of trap arms that connect to the horizontal wet vent must comply with the lengths shown in Table 10- 1. Table 7-5 states that the length of drainage piping is unlimited while the length of horizontal vents is limited to 1/3 of the total length allowed. (40 feet for 2 inch and 70 feet for 3 inch) It seems highly unlikely that these limits would be exceeded in a bathroom group.

Section 908.4.3 (2006), 908.2.1.2 (2009), 908.2.2 (2012) UPC allows four (4) DFU units on a 2 inch horizontal wet vent. The total DFU values affixed to a bathtub and lavatory is 3 DFU per Table 7-3 (2006/2009), Table 702.1 (2012). A 2” wet vent would be permissible by Code.

1. Yes. Based on a TIA that has been issued by IAPMO, for section 204.0, any combination of one water closet, one or two lavatories, and either one bathtub, or one combination bath/shower, and one shower, and, may include a bidet and an emergency floor drain, defines a bathroom group. Hence one water closet and one lavatory is “a combination of…”.
2. A. No. The code does not restrict a fixture from being plumbed conventionally, as long as they are fixtures that are defined as allowed in a bathroom group.
2. B. Yes. The code states “any combination.” of fixtures may be served by the horizontal wet vent. Note that lavatories with traps above the floor must be conventionally vented and may serve as the dry vent for the system.
3. Yes, the vent for the two lavatories would be considered a common vent and would be permitted to vent the bathroom group(s) provided they are the upstream fixtures or immediate downstream fixtures. For example; A tub or shower trap arm could be the upstream fixture with the two lavatories located immediately downstream to act as the vent for the bathroom group(s).

No. In August 2012 a TIA was issued by IAPMO to revise the language in the code regarding horizontal wet vents. Part of the change removed the mandatory language requiring all of the connections to the wet vent to be horizontal. New wording simply requires the connections to be above the weir of the trap and could be either horizontal or above the center line of the drain. The requirement for a vent to connect above the center line of the drain applies to all dry vents that connect to the horizontal wet vent or a horizontal fixture drain.

Once the vent becomes a dry vent it will need to meet the requirements found in Section 905.3, which states that “Unless prohibited by structural conditions, each vent shall rise vertically to a point not less than 6 inches above the flood-level rim of the fixture served before offsetting horizontally... Vents less than 6 inches above the flood-level rim of the fixture shall be installed with approved drainage fittings, materials, and grade to the drain.”

1. No. Only dry vent connections to the horizontal wet vent are required to have its invert taken off above the drainage centerline in accordance with Section 905.2.
2. All the piping and trap arms need to maintain the ¼” slope.

1. No. A water closet and any combination of a tub/shower, tub, shower, or 1 or 2 lavatories may be part of a wet vent installation. The key to a horizontal wet vent is that a fixture with a dry vent has a waste line appropriately sized to provide a vent for the horizontal wet vent piping system.
2. Yes, see answer 1
3. Yes, see answer 1
4. A dry vent, pertaining to a horizontal wet vent system, is the portion of the waste and vent piping for a lavatory(s), tub/shower, or tub, which is connected to the waste piping for the aforementioned fixtures and is located above the weir of the trap of that fixture. It is used to provide air for both the fixture and the horizontal wet vent piping system.

Horizontal wet venting is limited to any combination of fixtures within a bathroom group as defined in section 204.0

Section 910.3 of the UPC specifically requires the upper terminal vent for a combination waste and vent system to be connected to the waste piping downstream of the uppermost fixture. Figure 9-37 (2009), Figure 910.3A (2012/ 2015) in the Illustrated Training Manual is drawn per that requirement. Although not stated in the code, Figure 9-41 (2009), Figure 910.5B (2012/ 2015) shows that the maximum distance from the uppermost fixture trap to the vent to be 15 feet. Table 10-1 (2009), Table 1002.2 (2012/ 2015) shows allowable trap arm to vent distances for a standard waste and vent system.
Note: Only if Appendix B has been adopted, as specified in Section 103.8.2 (2009), 101.10 (2012), 102.8 (2015) would the provisions of Appendix B apply to the installation.

Yes, Section 908.2.1 of the 2015 UPC permits the dry vent for the horizontal wet vent to be an individual vent from a bidet, shower or bathtub as well as a lavatory. Drawings 1 and 3 appear to be code compliant.

Fittings for horizontally wet vented drainage systems are not required to be “taken off above the drainage centerline” as required for individually vented horizontal fixtures as found in Section 905.2 of the 2012 UPC. Without that requirement, the fixture may be connected to the run (straight through) or branch of the fitting.

The 2012 Uniform Plumbing Code does not address the installation of plumbing vents below solar panels. Good plumbing practice would suggest avoiding this type of installation. In the event there is no other solution to the problem there should be adequate space between the vent opening and solar panel to allow adequate air circulation in the DWV system as prescribed in Section 901.1. Plans should be submitted to the AHJ for approval as an alternate method of construction, to assure the installation meets the intent of the code.

1. No. The 6 foot length limitation for vertical wet venting is to ensure that the wet vented sections remains within a single story as required in Section 908.1 of the 2018 Uniform Plumbing Code.
2. Yes. Per Section 908.2.3, trap arms are limited to the lengths found in Table 1002.2. The Code has no other length limitations for horizontally wet vented bathroom groups.

It is the opinion of this Committee that the submitted illustration meets the intent of Section 911.0 of the 2015 Uniform Plumbing Code.

The floor drain is considered an emergency floor drain and is included in the definition of a bathroom group and if installed per Section 908.2 of the 2018 Uniform Plumbing Code, would not need to be individually vented.

1. Yes. The minimum drain size for the Laundry Tray(2DFU), per Table 703.2 of the 2018 Uniform Plumbing Code is 2”. Section 908.1 states that each wet-vented section shall be not less than one pipe sizing larger than the minimum pipe size required per Table 703.2. The required wet vent section would therefore be required to be 3”.
2. Yes. The wet-vented section and downstream piping is required to be 3”.

No. Section 905.3 of the 2015 Uniform Plumbing Code states that “Vents less than 6 inches above the flood-level rim of the plumbing fixtures it serves shall be installed with approved draining fittings, material, and grade to drain.” Sanitary Tees are only considered drainage fittings when installed in the vertical position.*

*2015 UPC, 706.2 Horizontal to Vertical. Horizontal drainage lines, connecting with a vertical stack, shall enter through 45 degree (0.79 rad) wye branches, 60 degree (1.05 rad) wye branches, combination wye and one-eighth bend branches, sanitary tee or sanitary tapped tee branches, or other approved fittings of equivalent sweep. No fitting having more than one inlet at the same level shall be used unless such fitting is constructed so that the discharge from one inlet cannot readily enter any other inlet. Double sanitary tees shall be permitted to be used where the barrel of the fitting is not less than two pipe sizes larger than the largest inlet, (pipe sizes recognized for this purpose are 2 inches, 21⁄2 inches, 3 inches, 31⁄2 inches, 4 inches, 41⁄2 inches, 5 inches, 6 inches, etc.) (50 mm, 65 mm, 80 mm, 90 mm, 100 mm, 115 mm, 125 mm, 150 mm, etc.).

1. No. The deletion of the stated language does not change the interpretation of Section 907.1 of the 2015 Uniform Plumbing Code. A drainage stack* less than 10 stories in length is not required to have a parallel vent stack with a yoke vent. Additionally, past interpretations of this section recognize horizontal offsets within the stack, regardless of the length of the offset, as a means of eliminating the need for the yoke vent.
2. No
*Stack. The vertical main of a system of soil, waste, or vent piping extending through one or more stories

Section 906.1 of the 2009 Uniform Plumbing Code (UPC) states, “Each vent pipe or stack shall extend through its flashing and shall terminate vertically not less than six (6) inches above the roof nor less than one (1) foot from any vertical surface”. Though the 2009 UPC does not define “flashing”, it can best be described as an impervious material that is used in building construction to prevent water from passing into a structure through an exterior penetration. Although flashings for plumbing vents are usually designed for roof penetrations, side wall flashings do exist. Vents penetrating the side wall of a structure, by means of a flashing, would be permitted if installed to the requirements found in Section 906.0.

No. Per Section 908.2.1 of the 2015 Uniform Plumbing Code, “Dry vent connections to the horizontal wet vent shall be in accordance with Section 905.2 and Section 905.3”. A dry vent would be required to meet both referenced code sections.

Yes, with the following conditions:
1. There is adequate space between the vent openings and grate to provide free movement of air as required in Section 901.2 and of the 2015 Uniform Plumbing Code.
2. The vent termination meets the requirements found in Section 906.1.
3. The opening on the upper portion of the walkway would require the vent locations, per Section 906.2, to be a minimum of 10 feet away from the walk-way or be raised as required in Section 906.3, to a minimum of 7 feet above the roof.

Note: This installation would not be acceptable in areas where snow or frost could cover the grates thereby restricting the circulation of air in the space between the roof and grate.

1. Yes. Section 911.5 of the 2015 Uniform Plumbing Code(UPC)states “fixtures other than the circuit-vented fixtures, are permitted to discharge to the horizontal branch drain. Such fixtures shall be located on the same floor as the circuit-vented fixtures and shall be either individually or common vented”.
2. Per Section 911.5, additional fixtures located on the same floor, may discharge either upstream or downstream of a circuit-vented branch. Waste piping receiving the discharge from fixtures on upper floors would be approved to be connected to the common waste line downstream of the circuit-vented branch.

1. No. The minimum size waste line downstream of the upper terminal vent would be 3” per Section 910.4 of the 2012 Uniform Plumbing Code*.
2. The 4” waste line after the upper terminal vent is larger than required by code. The purpose of the increase is twofold. 1) To eliminate the need for an additional vent that would be required at the 4” connection of the most downstream floor drain as required in the Section 910.3. 2) To provide only one 3-1/2” cleanout for the entire combination waste and vent system per Table 707.1.
3. Yes.
4. By definition, a trap arm is the “portion of a fixture drain between a trap and the vent”. The vent for a combination waste and vent system is the main waste line. The referenced pipe section therefore has two traps on one trap arm which conflicts with Section 1001.1, that permits only one trap per trap arm. By installing a vent on the uppermost fixture, over sizing the traps and drains, the installation would be considered a combination waste and vent system.
5. Since there are no length measurements on the piping, we must assume that the lengths are within the 15 foot limitation. The branch is considered a combination waste and vent system and as such shall meet the requirements of Section 910.3.

*Note: The entire combination waste and vent system has a drainage fixture unit load of 10 DFU. Each floor drain has a 3” trap which means the riser, being two pipe sizes smaller, would be 2”. A 2” floor drain, per Table 702.1 is 2 DFUs. Due to the oversizing requirements of the combination waste and vent system, the main waste line must be increased to 4” only after the last floor drain is connected to the system.

1. No. The purpose of a horizontal wet vent, is to permit multiple fixtures to be served by a common horizontal waste line* that also acts as the vent for the fixtures. The connection of fittings to a horizontal wet vented system, as indicated by the system’s description, are intended to remain horizontal. The water closet in this illustration is clearly installed on the vertical stack.
2. Yes. The fitting is not required to be rolled up to be code compliant. By definition, a fitting that is less than 45 degrees with the horizontal is still considered horizontal.

* Section 210.0 - Horizontal Pipe. A pipe or fitting that is installed in a horizontal position or which makes an angle of less than 45 degrees (0.79 rad) with the horizontal.

1. Yes. Section 905.3 of the 2015 Uniform Plumbing Code states that, “Vents less than 6 inches above the flood-level rim of the fixture shall be with approved drainage fittings, material, and grade to the drain”. Per Section 708.1, horizontal drainage pipe shall be run in a uniform slope of not less than 1/4 inch per foot to the point of disposal.
2. Although the Code does not specifically grant the Authority Having Jurisdiction (AHJ) the power to waive the requirements of the Code, deviation from the minimum slop of ¼ inch per foot slope for horizontal drainage pipe due to structural issues may, with the approval of the AHJ, warrant a onetime variance.

Yes. Section 911.0 of the 2018 Uniform Plumbing Code (UPC), does not specify the type or configuration of fixtures that are permitted to be installed on a circuit vented system.

Note: The 2021 UPC limits the fixtures installed on a circuit vent to water closets, showers, bathtubs, or floor drains. Additionally, when back-outlet or wall-hung water closets are installed on a circuit vented system provided no floor-outlet fixtures are connected to the same horizontal branch.

No. Section 1014.1.1 of the 2015 Uniform Plumbing Code, specifically states that “each fixture discharging into a grease interceptor shall be individually trapped and vented in an approved manner”.

Note: The 2021 UPC limits the fixtures installed on a circuit vent to water closets, showers, bathtubs, or floor drains.

No. The 2012 Uniform Plumbing Code, does not permit air admittance valves as an acceptable means of venting a drainage system. Section 901.1 requires air circulation throughout all parts of the drainage system by means “vent pipes installed in accordance with the requirements of this chapter and as otherwise required by this code”. This includes termination of each vent pipe through the roof as required in Section 905.4.

Note: Mechanical “check valve” type fittings allow air flow into the waste and vent system when the drain is flowing. Air is unable to flow out through these fittings, thus positive pressure generated downstream of the liquid flowing in the drain line is unable to escape through these “vents”. The purpose of a venting system is to allow air flow to occur in both directions, there stabilizing internal system pressures. Any fitting on a vent pipe which limits air flow to one direction conflicts with basic objectives of a vent piping system.

The sizing of both the drain and vent stack is determined by the number of fixture units being served by the stacks. The size of the yoke vent connection between the two stacks is controlled by the diameter of the smallest stack. Typically, the parallel vent stack will be larger than the drain stack at the upper floors. The diameter of the drain stack connection will then determine the size of the yoke vent connection. As the drainage stack increases in size, so the must the yoke vent connection.

No. Section 301.4 of the 2012 Uniform Plumbing Code does allow an alternate engineered design for plumbing system, but also states that the design shall comply with the intent of the provision of the code and shall provide an “equivalent level of strength, effectiveness, fire resistance, durability and safety”. Reducing the size of the vent from 2” (which is required per Table 703.2)to 1-1/2” will not provide an equivalent level of effectiveness.

Note: Jurisdictions that have adopted Appendix C (Alternate Plumbing Systems)may accept engineered plumbing systems sized per the requirements found in that appendix.

No. Section 908.2 of the 2018 Uniform Plumbing Code gives specific requirements for the installation of a horizontal wet vent for a bathroom group. By definition, a horizontal pipe is “a pipe or fitting that is installed in a horizontal position or which makes an angle of less than 45 degrees with the horizontal.” By using 45° fittings, the offset to the water closet is no longer horizontal but would be considered vertical.

The concrete slab may be the roof for the underground pump station, but the slab itself is located slightly above ground level. Permitting vents to terminate 12 inches above the slab would create a health hazard* for anyone in the vicinity of the pump station. Although the 2018 Uniform Plumbing Code does not specifically address this type of installation, Section 102.5 permits the Authority Having Jurisdiction the discretion to require alterations to plumbing systems to alleviate a nuisance or other dangerous or insanitary conditions that involves health or safety hazards.

Note: It is the opinion of this Committee that the requirements found in Section 906.4 would be the most applicable for this type of installation.

*Sewer gas includes hydrogen sulfide and ammonia. Sewer gas also contains methane, carbon dioxide, sulfur dioxide, and nitrous oxides

No. Section 905.3 of the 2015 Uniform Plumbing Code states that “Vents less than 6 inches above the flood-level rim of the plumbing fixtures it serves shall be installed with approved draining fittings, material, and grade to drain.” Sanitary Tees are only considered drainage fittings when installed in the vertical position.*

*2015 UPC, 706.2 Horizontal to Vertical. Horizontal drainage lines, connecting with a vertical stack, shall enter through 45 degree (0.79 rad) wye branches, 60 degree (1.05 rad) wye branches, combination wye and one-eighth bend branches, sanitary tee or sanitary tapped tee branches, or other approved fittings of equivalent sweep. No fitting having more than one inlet at the same level shall be used unless such fitting is constructed so that the discharge from one inlet cannot readily enter any other inlet. Double sanitary tees shall be permitted to be used where the barrel of the fitting is not less than two pipe sizes larger than the largest inlet, (pipe sizes recognized for this purpose are 2 inches, 2-1⁄2 inches, 3 inches, 3-1⁄2 inches, 4 inches, 4-1⁄2 inches, 5 inches, 6 inches, etc.) (50 mm, 65 mm, 80 mm, 90 mm, 100 mm, 115 mm, 125 mm, 150 mm, etc.).

1. Yes. Section 911.5 of the 2015 Uniform Plumbing Code(UPC)states “fixtures other than the circuit-vented fixtures, are permitted to discharge to the horizontal branch drain. Such fixtures shall be located on the same floor as the circuit-vented fixtures and shall be either individually or common vented”.
2. Per Section 911.5, additional fixtures located on the same floor, may discharge either upstream or downstream of a circuit-vented branch. Waste piping receiving the discharge from fixtures on upper floors would be approved to be connected to the common waste line downstream of the circuit-vented branch.

No. The 2012 Uniform Plumbing Code, does not permit air admittance valves as an acceptable means of venting a drainage system. Section 901.1 requires air circulation throughout all parts of the drainage system by means “vent pipes installed in accordance with the requirements of this chapter and as otherwise required by this code”. This includes termination of each vent pipe through the roof as required in Section 905.4.

Note: Mechanical “check valve” type fittings allow air flow into the waste and vent system when the drain is flowing. Air is unable to flow out through these fittings, thus positive pressure generated downstream of the liquid flowing in the drain line is unable to escape through these “vents”. The purpose of a venting system is to allow air flow to occur in both directions, there stabilizing internal system pressures. Any fitting on a vent pipe which limits air flow to one direction conflicts with basic objectives of a vent piping system.

1. Yes. Per Section 905.3 of the 2015 Uniform Plumbing Code (UPC), vents may have horizontal offsets if there are structural conditions prohibiting the vent from being installed vertically. Drainage fittings must be used and grade to the drain for all piping below the flood rim of the fixtures being served.
2. Yes. Section 907.2 requires the yoke vent connection to the drainage stack to be a wye-branch fitting. A combination wye & eighth fitting is a wye-branch fitting.
3. Yes. Section 907.2 does not specify the type of fitting required for the connection of the yoke vent to the vent stack. Section 903.1 requires vent pipe and fittings to comply with applicable standards referenced in Table 701.2.

1. Yes. Per Section 707.4(3) of the 2018 Uniform Plumbing Code (UPC), cleanouts may be omitted on all fixtures, except urinals, located above the floor level of the lowest floor of the building.
2. No. Section 707.4(3) does not specifically address cleanouts for sinks, including island sinks, therefore the cleanout on the foot vent would not be required.
3. No. Section 707.4(3) of the 2021 Uniform Plumbing Code (UPC) states, “Excepting the building drain, its horizontal branches, kitchen sinks and urinals, a cleanout shall not be required on a pipe or piping that is above the floor level of the lowest floor of the building”. The Code change would require a cleanout on the foot vent.

Gray water drains and sanitary drains are both waste water drains. The fixtures for both are required to be trapped and vented per applicable sections of the 2015 Uniform Plumbing Code. The Code does not prohibits the use of a common vent.

Circuit venting is an approved manner to vent up to a maximum of 8 fixtures such as water closets, floor drains, bathtubs and shower stalls. Restaurant equipment may not be circuit vented due to their grease producing potential. Per section 1014.1.1 of the 2015 UPC, each fixture discharging into a grease interceptor shall be individually trapped and vented in an approved manner. Also grease lines are not permitted to be a combination waste and vent system because of the type of grease waste migrating into the vents and thus affecting the venting.

Per Section 906.2 of the 2015 UPC, each vent shall terminate not less than 10 feet from, or not less than 3 feet above an openable window, door, opening, air intake, or vent shaft.

Per Section 909.1 of the 2015 UPC, pipe sizing for island drains “shall be as elsewhere in this code”. Sizing requirements for drainage and vent piping may be found in Tables 702.1 and 703.2. A domestic kitchen sink drain has an assigned drainage fixture unit value of two, requiring a minimum 2” waste line and 1-1/2” vent.
Note: The 2015 Illustrated Training Manual, Figure 909.1B shows a code compliant drawing of an island sink installation.

Yes, the fixtures allowed to be vented by a horizontal wet vent either have low discharge surges or last for only a short duration that do not significantly impact the air flow in the horizontal drain. That is why the water closet is distinguished from the other fixtures with the requirement to connect downstream of all the fixture drain connections to the horizontal wet vent.

No, The foot vent shall be taken off of the vertical fixture vent by means of a wye branch fitting immediately below the floor. The wye branch fitting connecting the return vent to the foot vent is to be in vertical position with the wye-branch sloping down toward the drain rather than up toward the vent, which would better assist air flow. A sanitary tee is a drainage fitting when installed in the vertical position, but it is connected to a trap arm and not allowable for the special venting of an island fixture.

No, the purpose of a horizontal wet vent is to permit multiple fixtures to be served by a common horizontal waste line, that also acts as the vent for the fixtures. The connection of fittings to a horizontal wet vented system, as indicated by the system’s description, are intended to remain horizontal, so as not to interfere with the continuous air space above the water surface in drain.