Bradford White TTW URG2PV75H6N Instructions Manual page 17

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 inches (30.5 cm) above the ground, or anticipated snow level, the
installation must be modified as shown below (see Figure 5). Refer to Table 3
for maximum venting lengths using 3 inch (7.6 cm) vent pipe or Table 4 for
maximum lengths using 4 inch (10.2 cm) vent pipe.
Figure 5
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