a 3" or 4" pipe from the outside. See Chapter 3.5 for
more direction on combustion air.
B To reduce pressure differentials between the exhaust
and combustion air intake, it is recommended that
both terminators exit on the same plane. See Fig. 14
for an example horizontal twin pipe termination and
Fig. 15 for the vertical twin pipe termination example.
Fig. 14 Horizontal twin pipe termination
Fig. 15 Vertical twin pipe termination
Warning: Failure to install a
condensate drain may result in damage
not covered by the manufacturer's
warranty. See chapter 3.6.3.
An approved vent terminator must be
used. See Table 5 for known approved
vertical vent terminations.
Any gas vent section that is greater than 45 degrees
from the vertical is considered horizontal. Horizontal
sections must slope upwards from heater at least ¼
inch for every foot of its horizontal length and be prop-
erly supported to allow condensate to be collected by
B No pipe joints other than the termination connections
should be exposed to the outdoors. See vent manu-
facturer instructions for details.
B Use of two 90° elbows (candy-cane) is an accepta-
ble termination for combustion air intake from the
roof. See Fig. 15 for an example.
B Screening (no smaller than 1/4" mesh) is recom-
mended on candy cane termination.
B Exhaust should terminate above and must be a mini-
mum of 3 feet from must intake termination.
B The exhaust vent must terminate above the roof sur-
face with an approved vent cap not less than 3 feet
(0.6 m) above the highest point where it passes
through the roof and at least 2 feet (0.6 m) higher
than any vertical wall or similar obstruction within 10
feet (3.1m). See Fig. 16 and Table 5.
Fig. 16 Vertical
(Combustion air piping not shown)
GAS VENT TERMINATIONS FOR LISTED VENT
Flat to 6/12
6/12 to 7/12
Over 7/12 to 8/12
Over 8/12 to 9/12
Over 9/12 to 10/12
Over 10/12 to 11/12
Over 11/12 to 12/12
Over 12/12 to 14/12
Over 14/12 to 16/12
Over 16/12 to 18/12
Over 18/12 to 20/12
Over 20/12 to 21/12
Table 5 Termination heights at various roof pitches
Interior masonry chimneys
The single wall stainless steel exhaust vent pipe must
be permanently mounted inside the masonry chimney.
6 720 608 263