Lochinvar RPD-I-S User Manual page 26

Venting continued-
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 maximum equivalent
length listed in these instructions.
2" VENT INSTALLATION
3" VENT INSTALLATION
Figure 13
26 RPD-I-S Rev A