PLUMBING VENTS

Air Admittance Valves

General Installation Requirements and Approved Uses
1. Install air admittance valves according to manufacturer’s installation instructions and provisions of the IRC.
2. You may use air admittance valves to vent individual vents, branch vents, circuit vents, and stack vents. Use individual and branch type air admittance valves to vent fixtures that are on the same floor level and that are connected to a horizontal branch drain.
3. Use air admittance valves that are rated for the vent size to which the valve is connected.
4. Install air admittance valves within 15

 

Circuit Vents

1. Fixture Types: Use a circuit vent to protect a combination of any fixture types.
2. Number of Fixtures: Use a circuit vent to protect not more than (≤) 8 fixtures. Read the full Topic

Combination Waste and Vent

1. Fixture Types: Use a combination waste and vent to protect floor drains, sinks, standpipes, and lavatory sinks. Do not connect toilets, urinals, or sinks with disposals to a combination waste and vent.
2. Number of Fixtures: Use a combination waste and vent to protect any number of approved fixture types.
3. Fixture Location: Use a vertical pipe not more than (≤) 8 feet high between the fixture drain and the horizontal combination waste and vent pipe.
4. Pipe Configuration:
(a) Slope the horizontal combination waste and vent pipe not more than (≤) one-half unit in twelve units (4 percent slope).
(b) Use Table P3111 to determine the size of the combination waste and vent pipe. Use the branch or stack column if the combination waste and vent pipe discharges into a horizontal branch or stack pipe. Use the building drain or subdrain column if the combination waste and vent pipe discharges into the building drain or a subdrain. See illustration on next page.   Read the full Topic

Common Vents

1. Fixture Types: Use a common vent to protect any two fixtures. You may common vent different types of fixtures, such as a sink and a shower or a shower and a toilet.
2. Number of Fixtures: Use a common vent to protect only two fixtures.
3. Fixture Location: Use a common vent only for fixtures located on the same floor level. You may connect the fixture drains at different vertical levels if the fixtures are on the same floor level.
4. Horizontal Common Vent Connection Location: You may connect the common vent where the fixture drains intersect. You may connect the common vent downstream from where the fixture drains intersect only when the fixture drains connect to the branch drain pipe at the same horizontal level.
5. Vertical Common Vent Connection Location: Connect the common vent as a vertical extension of the branch drain pipe when the fixture drains connect to the branch drain pipe at different vertical levels. Do not connect a toilet above another type of fixture when connecting two fixtures to a vertical common vent.
6. Fixture Drain Length to Vent Connection: Use Table P3105 to determine the maximum distance between each fixture trap weir and the common vent fitting.
7. Common Vent Pipe Size: (a) Use at least a (≥) 1 ¼ inches pipe or a pipe at least (≥) one-half the size of the drain pipe being vented, whichever is larger, for the common vent. (b) Use the following table to size the vertical pipe between the upper and lower fixture drain connections of a vertical common vent. Use the total dfu discharged by both         fixtures and Table P3005.4-1 to size the vertical pipe below the lower fixture drain connection of a common vertical vent. You may not connect a toilet to a drainage pipe smaller than 3 inches regardless of what is allowed in the table.

Fixture Drains

Vent Distance from Trap
1. Use the following table to determine the maximum length of a fixture drain between a trap weir and a vent fitting. The vent fitting may be at a vent pipe, such as an individual vent, or at a vented pipe, such as a wet vent.
2. The table does not apply to self-siphoning fixtures, such as toilets. No fixture drain length limitations apply to these fixtures.

Fixture Drain Slope
1. Connect the fixture drain pipe with not more than (≤) one pipe diameter of fall between the bottom of the trap outlet and the bottom of the vent fitting inlet. This parallels the distance requirements in Table P3105 and reduces the chance that the trap will drain because the fitting is below the trap. Example: 5 feet x ¼ inch/foot = 1 ¼ inches. See the first row of Table P3105.
2. Connect the top of the fixture drain pipe to the vent fitting above trap weir. This provision does not apply to toilet fixture drains. See illustration on next page.

Crown Venting
1. Connect the vent fitting at least (≥) two pipe diameters from the trap weir.

Individual Vents

1. Fixture Types: Use an individual vent to protect any fixture.
2. Number of Fixtures: Use an individual vent to protect only one fixture.
3. Fixture Location: Use an individual vent to protect one fixture located anywhere in the structure.
4. Individual Vent Connection Location: Connect the individual vent on the fixture drain of the fixture being vented or at the fixture drain connection to the drainage system.
5. Fixture Drain Length to Vent Connection: Use Table P3105 to determine the maximum distance between the fixture trap weir and the individual vent fitting.
6. Individual Vent Pipe Size: Use at least a (≥) 1 ¼ inches pipe or a pipe at least (≥) one-half the size of the drain pipe being vented, whichever is larger.

Island Fixture Vent

1. Fixture Types: Use an island fixture vent to protect only sinks and lavatories. You may connect a dishwasher and disposal to a kitchen sink as a kitchen group.
2. Number of Fixtures: Use an island fixture vent to protect any number of approved fixtures types.
3. Fixture Location: Use an island fixture vent only for fixtures located in the same island and on the same floor level.
4. Pipe Configuration:
(a) Extend the loop portion of the island fixture vent vertically to above the drain outlet of the fixture being vented before extending the horizontal and vertical downward portion.
(b) Use drainage fittings and pipe slopes for any portion of the vent below the fixture flood rim level. Do not use vent fittings or slope the vent pipe as a vent below the fixture flood rim level.
(c) Connect the downward portion of the vent loop downstream from where the fixture drain connects with the horizontal drainage pipe. Make the connection using a full size fitting.
(d) Provide cleanouts at the downward portion of the loop vent and in the vertical portion of the vent pipe before it connects to the exterior vent pipe. Read the full Topic

Plumbing Vents General Installation

Plumbing Vents Required
1. Install an approved vent for every trap and trapped fixture. This means that every plumbing fixture (such as a sink or a shower) and every plumbing fi xture with an integrated trap (such as a toilet) must be protected by an individual vent or an approved system where one vent protects multiple fixtures.
2. Terminate at least (≥) one vent outdoors. Connect the outdoor vent to the building drain or to a branch or extension of the building drain. The branch or extension cannot be an island fixture vent.

Flood Resistance
1. Install vent pipes above the design flood elevation established by local regulations. Obtain this elevation from Section R323.1 or from the local building official.

Vent Slope and Support
1. Install all vent pipes using adequate supports so that the vent pipes slope toward the soil or waste pipe. Moisture in any form should fl ow toward the soil or waste pipe by gravity. The IRC does not specify support intervals for vent pipes. Supporting vent pipes at the same interval required for drain pipes is recommended, but not required.

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Vent Exterior Terminations

Vent Height Above Roof
1. Extend vent pipes above the roof at least (≥) 6 inches, or the number of inches required by local snow accumulation and temperature conditions, whichever is higher. Measure height on the high side where the vent exits the roof. Obtain the snow accumulation height from the local building official.
2. Extend vent pipes at least (≥) 7 feet above any roof used as a balcony, observation deck, or similar accessible walking surface.

Vent Freezing and Frost Closure Protection
1. Protect exterior vent terminals from freezing by using heat, insulation or both.
2. Increase the diameter of exterior vent terminal pipes to at least (≥) 3 inches, beginning at least (≥) 1 foot below the roof or inside the wall.
3. These provisions apply only where the 97.5 percent winter design temperature is less than (<) 0° F. Obtain this information from IRC Chapter 3 and from the local building official. Read the full Topic

Vent Pipe Size

Vent Pipe Size
1. Use at least a (≥) 1 ¼ inches diameter vent pipe or a vent pipe at least (≥) one-half the diameter of the drain pipe being vented, whichever is larger, as the dry vent.
2. Increase the vent pipe diameter by at least (≥) one pipe size over the entire length of the vent pipe when the vent developed length is greater than (>) 40 feet.

Vent Pipe Developed Length
1. Measure the developed length of individual, branch, and circuit vents beginning where the vent connects to the drainage system and ending where the vent connects to a vent stack, stack vent, air admittance valve, or the vent’s termination point outside the building.

 

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Waste Stack Vents

1. Fixture Types: Use a waste stack vent to protect any combination of fixtures, except toilets and urinals.
2. Number of Fixtures: Use a waste stack vent to protect any number of approved fixture types.
3. Fixture Location: Use a waste stack vent for fixtures located on the same or different floor levels.
4. Pipe Configuration:
(a) Use only a vertical pipe for a waste stack. Do not install vertical or horizontal off sets in the waste stack pipe between the highest and lowest vented fixtures. You may install offsets in the vertical pipe below the lowest fixture vented by the waste stack vent.
(b) Maintain at least (≥) the same pipe size for the entire length of the waste stack.
(c) Connect each fixture separately to the waste stack. Read the full Topic

Wet Vents

1. Fixture Types: Use a wet vent to protect any combination of fixtures from not more than (≤) two bathroom groups.
2. Number of Fixtures: Use a wet vent to protect not more than (≤) two toilets, and two bathtubs or showers, and two lavatory sinks, and two bidets.
3. Fixture Location: Use a wet vent only for approved bathroom fixtures located on the same floor level.
4. Wet Vent Connection Location:
(a) Begin the wet vent with an individual or common vent for a lavatory, bidet, shower, or bathtub. This vent does not need to be at the first wet vented fixture in a horizontal wet vent. This vent must be at the first wet vented fixture in a vertical wet vent. End the wet vent at the last wet vented fixture connection to the wet vented pipe.
(b) Do not connect more than one fixture upstream from the beginning individual or common vent in a horizontal wet vent.
(c) Connect each fixture individually to the wet vented pipe. Do not connect two or more fixtures together and connect that branch drain to the wet vented pipe. Read the full Topic