Bradford White TTW URG2PV75H6N Instructions Manual page 16

Venting continued-
THROUGH THE ROOF VENTING: (VERTICAL VENTING)
Cut the necessary holes through the roof and ceiling and install the vent
connector as shown in Figure 4. Make sure that the installation meets the local
codes and/or The National Fuel Gas Code ANSI Z223.1 (Latest Edition) or
CGA/CAN B149 Installation Code (latest edition).
Figure 4
NOTE: For installations requiring both horizontal and vertical runs, the
following rule must be followed: Total length of straight pipe (both
horizontally and vertically) must not exceed the allowable length listed in
the "Through The Wall" section of the table for total number of elbows
used.
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