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Tankless Heater in Interior Space

Rod Kotiga
Rod Kotiga Member Posts: 68
It might end up pricey because the flue pipe for your old water heater and flash type are two different types. Most flash water heater co. want stainless steel class three pipe ($$$$) and some you can use a pvc that is solid core. Either way b- vent can rot out due to the flue gas condensation and I'm assuming that's what you have now servicing your normal w.h. Also all that vertical pipe and your definatley going to have to install a condensate tee near the flash w.h. Try to get a unit that works with pvc since it's a lot easier to work with and will probably mean a more eff. w.h.


  • Paul Townsley
    Paul Townsley Member Posts: 1
    Tankless Heater in Interior Space

    I have a gas fired tank type hot water heater located in an enclosed space that is NOT adjacent to an outside wall of the house. The combustion air and flue gas for the hot water heater are ducted upwards through the attic and out. I want to retrofit a tankless hot water heater in the same space but am concerned that having vertical ducts for the exhaust gas and intake air will not work. Obviously ducting the heater to the side wall of the house is not an option here. Are there solutions for this type of application?
  • Steven Eayrs
    Steven Eayrs Member Posts: 33
    Follow the directions........

    Most of the sealed combustion, on-demand, wall vented water heaters have a thru the roof optional kit, and will guide you thru the details. If over a certain distance they will most likely recommend a condensate collector, which will drain the condensate off, before it would otherwise run back into the heater.
    Don't decide to get cheap or use other than the recommended stack material. Could kill ya.!!
  • Mike Thomas_2
    Mike Thomas_2 Member Posts: 109
    Drain Needed

    And don't forget this condensate will need to be directed to a floor drain, and local code may require you to neutralize the condensate before it goes down the drain. If you don't have a drain in there, better figure out how your going to get one....
  • Rich Kontny_3
    Rich Kontny_3 Member Posts: 562
    Navien America

    Has a high eficiency model that has plastic as an intake and exhaust option. Condensate is an issue however. Go to navienamerica .com
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