Condensing Tankless Water Heater Venting Material (ABS, PVC, or CPVC)

Discussion in 'Tankless Water Heater Forum' started by janderson13, Sep 22, 2013.

  1. janderson13

    janderson13 New Member

    Sep 20, 2013
    Spokane, Wa

    I plan to install a Takagi tankless heater

    I'm confused as to what piping I should be using. I was planning to use ABS as the manual says that is ok as long as it can withstand 149 degrees F, is NOT foam core, and is ASTM D2661 compliant. I look at Home Depot and Lowes and they carry Charlotte ABS cellular core pipe (appears to be foam core), they say it has a heat rating of like 160 degrees F, and conforms to ASTM D2661. I realize that this appears to be foam core. I look at Charlotte's site and it says the pipe is only rated for 140 degrees F and is infact foam core, but that it is designed for venting applications.

    So... I look at my furance venting that is done in ABS and it is using the same Charlotte ABS cellular core pipe - I'm starting to wonder if this is dangerous now? Or does the furnace allow for a lower specification of pipe?

    I thought I would look for CPVC and they don't seem to carry that. I'll try Furgeson on Monday for the CPVP.

    I'm wondering what other people are using and if I should replace my furnace pipe. The time to do it is now because we are finishing our basement.


  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    The issue is how it reacts when it does get hot...a solid core product typically will stay firmer and not distort or sag (as much). The horizontal runs do need to be supported properly, and that helps minimize any issues. The existing pipe should have some markings on it which would allow you to verify if it is proper. If not, yes, I'd replace it while you have it open.
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