I'm in the process of a major bathroom remodel. As part of the project I'm planning on switching the house over from a tanked water heater to a tankless unit from Rheem. I really like the features of the Rheem condensing units, but I'm a little confused on how to vent the unit.

For starters, the condensing units say I can use PVC piping for the intake and exhaust. That's great, but I'm not sure if that will meet code in CA. Also my current water heater vents straight up through the roof from an enclosure that inset in the back of the house. I plan on mounting the tankless in the same cabinet and venting nearly straight up through the roof. Do tankless units require that I have a horizontal run of piping with a condensate trap? Can I use a condensate trap in a vertical configuration?

Last, I see that Rheem offers a PVC concentric vent termination pipe (2 into 1) that says it can be used for vertical applications. I have yet to see a picture of this pipe in a vertical application, so I'm not sure what is acceptable to use to cap the pipe. It appears that the top of the vent is open to free air, which is the exhaust side of the concentric pipe.

Anybody ever use one of these? Any insight on the condensate trap problem? Should I just switch over to the standard model and use the dual wall stainless piping?


PVC vent termination pipe in question..

Planned Rheem RTGH-84DVN Condensing unit for a 2 bath house.