Bradford White PDX1-40S6FBN Installation And Operating Instruction Manual page 34

Venting continued-
THROUGH THE WALL VENTING WITH LOW GROUND CLEARANCE:
When venting cannot exit through the wall at a height greater than or equal to
12" (30.5 cm) above the ground, or anticipated snow level, the installation must
be modified as shown below (see Figure 15). Refer to Table 3 for maximum
venting lengths using 2" (5.1 cm) vent pipe or Table 4 for maximum lengths
using 3" (7.6 cm) vent pipe. The exhaust and intake terminals must not be less
than 16 in. (40.6 cm) apart (see figure 11a).
Figure 15
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