Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Condensate from atmospheric boiler

Jimbo_5 Member Posts: 218
I cannot help but wonder, my boiler (WM CGi-3) has a long exhaust vent (20') and the condensation runs back pretty strong.  But is there a "difference" between this condensation and the condensate produced by a mod/con?  I mean, does this condensation need to be neutralized prior to dumping in an old CI drain line?


  • Ironman
    Ironman Member Posts: 6,856

    There shouldn't be any noticeable amount of condensation from an atmospheric boiler. Your boiler return temp is probably too low or the burner is under-firing because the gas pressure is too low on the manifold.

    And the condensate is exactly the same as from a mod/con - it's acidic.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • EricAune
    EricAune Member Posts: 432

    Does your boiler vent through the side wall of the house with assistance from a fan/blower? Stainless steel venting with a condensate tee on the horizontal vent pipe just before the boiler?

    If this is the case, and you are getting a steady flow of condensate then yes the fluid is corrosive to cast iron drain piping. 

    The long vent length is likely to be the cause of the large amount of condensate, however, you should have boiler return water temperatures above the 140*F range.  If your temperature is lower than that there are also issues with condensing on the outside of the boiler heat exchanger, that would have to be fixed for safety and the health or your boiler.
    "If you don't like change, your going to like irrelevance even less"
  • Jimbo_5
    Jimbo_5 Member Posts: 218
    My error . . ..

    Yes, the CGi is fan induced, and the exhaust vent runs through an unheated crawl space, maybe 20 feet or so.  The original installer drilled a hole in the cement floor, inserted a piece of 3/4-tubing and let it rip.  I was concerned about damaging either the concrete or creating an ever-growing hole beneath the basement floor.  So we put a pump on it, which dumps into old service-grade CI at the slop sink.  Now I'm wondering if the floor outlet wasn't such a bad idea.
  • Ironman
    Ironman Member Posts: 6,856

    The Vent pipe in the crawl space to keep the temp up and reduce condensation. And check your boiler return temp. If you have outdoor reset, Adjust the baseline temp to 140 deg.

    Also, Is that single wall pipe in the crawl space? If it is, that's a code violation unless it a venting system approved by the manufacturer.

    You should not have any substantial condensation in the vent.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
This discussion has been closed.