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4. Install vent pipe so that it can expand and contract
freely as the temperature changes. Support the vent
pipe according to applicable codes and vent manufac-
turer’s instructions. Pipe support must allow the vent
pipe free movement out and back, from side to side, or
up and down as necessary, without putting a strain on
the heater or vent body. Slope horizontal pipe runs up
from the heater at least 1/4” per foot. Install Listed con-
densate drains at low points where condensate might
collect. Plumb condensate drains to a drain through
hard piping or high-temperature tubing such as sili-
cone rubber or EPDM rubber – do not use vinyl or
other low temperature tubing. Follow drain manufac-
turer’s installation instructions.
5. Use Listed firestops for floor and ceiling penetrations.
Use Listed thimble for wall penetrations. Use a Listed
roof flashing, roof jack, or roof thimble for all roof pen-
etrations. Do not fill the space around the vent (that is,
the clear air space in the thimble or firestop) with
insulation. The roof opening must be located so that
the vent is vertical.
6. Vent Termination – Vertical (See Table 4, Page 13, for
height of vent termination above the roof. See Table 7,
Page 15, for Listed terminations.) Use a Listed vent ter-
minal specified by local and national codes and your
manufacturer’s instructions. A roof termination must be
vertical.
7. Vent Termination – Horizontal (See Table 7). Use a list-
ed wall thimble and vent terminal from Table 7.
The terminal must be located (see Figure 13):
• at least 3” and at most 12” out from the wall (see Figure
14), following the vent manufacturer’s instructions.
• at least 12” above finished grade or the normally
expected snow accumulation level, whichever is higher
14
Brand Manufacturer Material Type Sealant
Saf-T Vent
®
4” Heat-Fab, Inc. Metal Consult Manufacturer
Special Gas Vent 38 Hayward Street
(Single Wall) Greenfield, MA 01301
(800) 772-0739
Saf-T CI Vent
®
Heat-Fab, Inc. Metal Consult Manufacturer
Special Gas Vent 38 Hayward Street
(Double Wall) Greenfield, MA 01301
(800) 772-0739
Z-Vent 4” Special Z-Flex U.S., Inc. Metal G.E. RTV 106
Gas Vent (Type BH), 20 Commerce Park North
Model SVE Bedrford, NH 03110-6911
(800) 654-5600
Table 5: Recommended Special Gas Vents (Positive Pressure)
1' Min.
4' Min.
4' Min.
4' Min.
4' Min.
3' Minimum clearance if
horizontal distance to
exhaust opening is less
than 10 feet.
Forced Air
Inlet
Vent
Termination
1' Minimum
above snow or
finished grade
(whichever is
higher)
At least 7'
above grade
adjacent
to public
walkways
Vent
Termination
Vent
Termination
Gas Meter
Max 12"
Min 3"
FIGURE 13: Minimum exhaust vent clearances. Local codes may differ - consult local code officials.