PVC or CPVC vent pipe on tankless heater?

[Daniel Leung]

I need heating/plumbing experts' comments. Can you see the problem on these vent pipe materials in a new house in Canada?

When checking the page 34 of installation manual (http://www.navienamerica.com/PDS/ftp/CombiGasWaterHeaters/Installation_Manual/CombiBoiler(CH)_Installation.pdf), it recommended Type-BH Class IIB (PVC) in Canada. Is it an error of CPVC?

I am not a plumber, but I think IIA is white PVC up to 65ºC(150ºF) and IIB is grey CPVC up to 90ºC(195ºF). Also I think PVC and CPVC vent pipe cannot be mixed together other than using the CPVC glue. Please correct me if wrong.

[John Dirks Jr]

The manual says recommended. It does not say required.

My non-expert opinion is it would be unlikely that any problems would result from the use of that grey CPVC section used for venting that WH.