The EZ models can each vent using dual- 2 or 3 inch single-pipe (PVC or CPVC) as well as 2-inch Flex, which can be fed through the existing B-Vent — again saving time and material. (Note: The choice of a single-pipe versus a dual-pipe configuration will depend on the air quality of the particular application.) In another first, multiple-unit installations for very large applications can reduce costs through common venting