17
How to Read the Venting Chart
The chart below applies to co-axial roof or wall
termination.
1. The total length of the vent pipe cannot exceed
40 feet.
2. The minimum vertical height with roof termination is
6 feet.
3. Any combination of rise and run can be used as
long as they are within the allowable limits shown
on the chart below.
4. A maximum of 4 x 90 degrees elbows—or
equivalent (2 x 45 degrees = 90 degrees)—can be
used.
5. Each 90 degrees elbow installed on the horizontal
plane is equivalent to a 3 feet horizontal pipe;
therefore, 3 feet must be subtracted from allowable
horizontal run. (45 degrees elbow is equivalent to
18 inches horizontal pipe.)
6. All horizontal pipe runs must be graded 1/4 inch per
foot upwards in the direction of the exhaust
fl
ow.
The
fi
nal pipe length, when terminating through the
wall may be graded downwards slightly to prevent
water migration.
7. A restrictor is required for all installations—see next
section.
2
4
6
8
10
12
14
16
18
20
Example 1
V Value = V1 (6’) + V2 (6’) + V3 (2’)= 14’
H Value = H1 (3’) + H2 (3’) = 6’
#2 Restrictor position required
VERTICAL
RISE (ft)
HORIZONTAL RUN (ft)
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
Venting Chart
4 x 90º ELBOWS
MAXIMUM (or equivalent)
#4 Restrictor
Example 1
NO INSTALLATION
NO INSTALLATION
Min. 2’
before
elbow
MINIMUM
VERTICAL
RISE: 2’
V1
V2
V3
H1
H2
Min. 12” pipe
Max. 24” pipe if
min. vertical rise
is used
45° elbow directly
on flue collar
Max. 6” pipe if
min. vertical
rise is used
1” min.
all around
vertical pipe
3” min.
above top of
horizontal pipe
1” min. around
bottom & sides of
horizontal pipe
#3 Restrictor
#2 Restrictor
#1 Restrictor
Allowable Co-Axial
Vent Confi gurations
Co-Axial Venting
INSTALLATION
