A.O. Smith XDVS - Manual (Page 7)

7
FLUE EXTENSIONS
There are three optional extension kits available. Any
combination of the three kits can be chosen; however, only one
kit can be used vertically and/or horizontally, see Figures 10
and 11.
WARNING
At no time can more than one Vertical and/or one Horizontal
Vent Kit be used.
Unless otherwise specified at the time of ordering, a standard
extension kit is individually packaged and shipped within the
water heater carton.
POSSIBLE EXTENSION COMBINATIONS
FIGURE 10
FIGURE 11
FIGURE 6
FIGURE 7
FIGURE 8
FIGURE 9