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Navien flow out condensate line

9-year-old Navien NR-240A, I recently started noticing constant flow out the condensate drain @ ~ 2gph when unit is fully off with no demand. The unit is configured for scheduled recirculate times. The flow only occurs during programmed "off" periods, but not always. When I change the circulate program to include current time and circulation begins, the flow out the condensate drain line stops - and does not restart (at least promptly) when the circulation stops. Peculiar. Navien help service said "this is odd. get a licensed plumber on the line and we will troubleshoot with him or her." I'm not that desperate, yet. Any advice?


  • Jamie Hall
    Jamie Hall Member Posts: 23,657
    It is odd, and Navien's advice is excellent. My first WAG is going to be leaking seal in the circulation system...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • DZoro
    DZoro Member Posts: 1,048
    Post some pictures of the system
  • Gordy
    Gordy Member Posts: 9,546
    sounds like a leak if it’s doing it while the boiler is idle.
  • dawark
    dawark Member Posts: 1
    I'm a master plumber I own a plumbing company in Houston texas... All we do is work on tankless water heaters and boilers we're an authorized technician for navien that being said that's a very common problem with navient heaters but it's also a very simple fix... It's a bad o-ring on an inlet or an outlet of the heat exchanger....
  • allanlo
    allanlo Member Posts: 1
    Thanks Dawark, you were right. The O-ring between the flow sensor on the inlet was bad. Replaced it and the problem was resolved. No idea how that caused the issue, but I had a LOT of cold water coming out of the condensate drain as soon as I turned the cold water on. Boiler was unplugged at the time.
  • joeba
    joeba Member Posts: 24
    Allan, can you post a pix of the Navien where you changed the O ring? I also own a 10 Yo NR240A and if this happens I want to be prepared. Replacement part # would also be helpful.