Rinnai Tankless RC98HPi Venting using PVC vs concentric pipe

Discussion in 'Tankless Water Heater Forum' started by Greer, Mar 9, 2020.

  1. Greer

    Greer New Member

    Joined:
    Mar 9, 2020
    Location:
    Salt Lake City, Utah
    I have a Rinnai RC98HPi tankless water heater that was installed about 10 years ago. It is vented out the back wall using a horizontal termination pipe. I am installing a window just above the exhaust so I need to run the exhaust up through the roof instead.

    Do I have to use the concentric pipe form Rinnai or can I use an adapter like Rinnai's Twin Pipe Adapter and then use two 3" PVC pipes? Maybe a third party vent through the roof using 3" PVC?

    There is a standard 2x4 wall straight above the water heater that I need to run the pipes through and concentric pipe is too big so I'll have to make modifications to that wall. If I can use 3" PVC it will save me a tone a of work but I want to do it correctly - no shortcuts.

    The manual for the Rinnai's Twin Pipe Adapter says it is only for the RU98 but I'm not sure if that's just because the RC98 is old or if it will work correctly with the RC98.

    Any thoughts/suggestions greatly appreciated!
     
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