Transcript Slide 1

PLUMBING VENTS
A vent is simply described as a device that can take
unwanted air from one place and deposit it somewhere
else, usually outside.
A plumbing vent does two essential things. It provides
an escape for toxic gas from a sewage system into the
atmosphere. It also provides a channel for a source of air
to replace effluent that moves through drain pipes, in order
to replace the air displaced by the waste.
In this manner, the air pressure within the waste
system remains consistent, so the fluid that collects in the
trap of a fixture is not sucked out by siphon action.
Notice in the vent size chart there are three things that
must be known in order to select the proper size for a vent;
Size of drain that serves the particular vent,
Fixture Units served by the vent, and
Length of vent
LAVATORY
WC
3'
2'
2'
SINK
3'
WASHER
SHOWER
3"
2"
12'
3'
2"
2"
WATER HEATER
2"
Notice in the elevation diagram of the plumbing group
for the residence where the kitchen adjoins the bath room
and utility room.
Consider the vent that extends through the roof from
the water closet.
First, it serves all the fixtures, which equals 13 fixture
units.
The drain size that serves this vent is 3”
The length of the vent is 12’ more or less.
Go to the chart and find the first 3” drain at the left
column, then move to the right and see that this particular
one will serve only 10 fixture units. Since we have 13
fixture units, go to the next 3” drain below, and see that it
will serve 30 fixture units. Since we have only 13 that line
is OK. Then move to the right in the body of the chart and
see the column under the 2” vent size and read the number
60. That means the 2” vent will serve the 13 fixture units
with a 3” drain if the vent is not longer than 60 feet. So a
2” vent is proper for this application.
Consider the multistory diagram from your packet, page
40. Fixture unit values for fixtures in this diagram are
taken from the top of page 43, “Design of Waste Drainage
and Venting for a multistory assembly.”
WC
=
6
Urinal
=
6
Lavatory
=
1
Service Sink =
2
Floor drain =
1
The elevation is of a plumbing group back to back, so the
fixtures in the diagram actually represent 2 fixtures back to
back, attached to the drainage system.
Fixture unit values
are shown as they
accumulate downward.
12
12
30
The dashed lines
represent vents.
Notice particularly
the vent line that is
adjacent to the main
vertical drain – It is
called a revent as
a vertical drain
cannot be used as
a vent.
60
90
121
2
22
2
scratch