Page 95 - 2018_IPC

VENTS

TABLE 913.4 The relief vent shall be installed in accordance with Sec-
WASTE STACK VENT SIZE tion 905.
MAXIMUM NUMBER OF DRAINAGE FIXTURE UNITS
(dfu) 914.4.2 Fixture drain or branch. The relief vent is per-
STACK SIZE Total discharge into one mitted to be a fixture drain or fixture branch for fixtures
(inches) branch interval Total discharge for stack located within the same branch interval as the circuit-
1
1 / 2 1 2 vented horizontal branch. The maximum discharge to a
2 2 4 relief vent shall be four fixture units.
1
2 / 2 No limit 8 914.5 Additional fixtures. Fixtures, other than the circuit-
3 No limit 24 vented fixtures, are permitted to discharge to the horizontal
4 No limit 50 branch drain. Such fixtures shall be located on the same floor
as the circuit-vented fixtures and shall be either individually
5 No limit 75
or common vented.
6 No limit 100
For SI: 1 inch = 25.4 mm.
SECTION 915
COMBINATION WASTE AND VENT SYSTEM
SECTION 914
CIRCUIT VENTING 915.1 Type of fixtures. A combination waste and vent sys-
tem shall not serve fixtures other than floor drains, sinks, lav-
914.1 Circuit vent permitted. Not more than eight fixtures atories and drinking fountains. Combination waste and vent
connected to a horizontal branch drain shall be permitted to systems shall not receive the discharge from a food waste dis-
be circuit vented. Each fixture drain shall connect horizon- poser or clinical sink.
tally to the horizontal branch being circuit vented. The hori-
zontal branch drain shall be classified as a vent from the 915.2 Installation. The only vertical pipe of a combination
most downstream fixture drain connection to the most waste and vent system shall be the connection between the
upstream fixture drain connection to the horizontal branch. fixture drain and the horizontal combination waste and vent
pipe. The vertical distance shall not exceed 8 feet (2438 mm).
914.1.1 Multiple circuit-vented branches. Circuit- 915.2.1 Slope. The slope of a horizontal combination
vented horizontal branch drains are permitted to be con- waste and vent pipe shall not exceed one-half unit vertical
nected together. Each group of not more than eight fix- in 12 units horizontal (4-percent slope) and shall be not
tures shall be considered to be a separate circuit vent and less than that indicated in Table 704.1.
shall conform to the requirements of this section.
915.2.2 Size and length. The size of a combination waste
914.2 Vent connection. The circuit vent connection shall be and vent pipe shall be not less than that indicated in Table
located between the two most upstream fixture drains. The 915.2.2. The horizontal length of a combination waste and
vent shall connect to the horizontal branch and shall be vent system shall be unlimited.
installed in accordance with Section 905. The circuit vent
pipe shall not receive the discharge of any soil or waste. TABLE 915.2.2
SIZE OF COMBINATION WASTE AND VENT PIPE
914.3 Slope and size of horizontal branch. The slope of the MAXIMUM NUMBER OF DRAINAGE
vent section of the horizontal branch drain shall be not FIXTURE UNITS (dfu)
greater than one unit vertical in 12 units horizontal (8.3-per- DIAMETER Connecting to a horizontal Connecting to a building
cent slope). The entire length of the vent section of the hori- PIPE (inches) branch or stack drain or building subdrain
zontal branch drain shall be sized for the total drainage 2 3 4
1
discharge to the branch. 2 / 2 6 26
914.3.1 Size of multiple circuit vent. Each separate cir- 3 12 31
cuit-vented horizontal branch that is interconnected shall 4 20 50
be sized independently in accordance with Section 914.3. 5 160 250
The downstream circuit-vented horizontal branch shall be 6 360 575
sized for the total discharge into the branch, including the
For SI: 1 inch = 25.4 mm.
upstream branches and the fixtures within the branch.
915.2.3 Connection. The combination waste and vent sys-
914.4 Relief vent. A relief vent shall be provided for circuit-
tem shall be provided with a dry vent connected at any
vented horizontal branches receiving the discharge of four or point within the system or the system shall connect to a
more water closets and connecting to a drainage stack that horizontal drain that serves vented fixtures located on the
receives the discharge of soil or waste from upper horizontal
same floor. Combination waste and vent systems connect-
branches.
ing to building drains receiving only the discharge from
914.4.1 Connection and installation. The relief vent shall one or more stacks shall be provided with a dry vent. The
connect to the horizontal branch drain between the stack vent connection to the combination waste and vent pipe
and the most downstream fixture drain of the circuit vent. shall extend vertically to a point not less than 6 inches

78 2018 INTERNATIONAL PLUMBING CODE ®
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