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.

test holes for gas condensing boilers/furnaces

Paul_69 Member Posts: 251
When testing gas high eff. units and the manufactuer does not provide a test port,how can you safely drill and plug a hole in venting so it cant blow out fumes/co etc.? In Mass. is there a code against this. Thx in advance


  • SWEI
    SWEI Member Posts: 7,356
    On positive pressure PVC and CPVC exhaust vents, we drill and tap an 1/8" NPT hole and install a brass plug.

    On natural draft and induced draft flues, we used to thread in a fat sheet metal screw or cover with aluminum tape, but in Jim's CO class I learned even that is unnecessary.
  • bnjmn
    bnjmn Member Posts: 53
    How long do your brass plugs last with the acidic condensate?
  • Henry
    Henry Member Posts: 996
    edited March 2016
    One can buy 1/4 PVC threaded plugs but it could be a pain to get. 1/4 inch S/S plugs are what we use.
  • SWEI
    SWEI Member Posts: 7,356
    bnjmn said:

    How long do your brass plugs last with the acidic condensate?

    Haven't seen any issues, but they are in a vertical section and not on the side where most of the condensate flows. We'll switch to stainless when the brass ones are gone. It's actually cheaper than brass.
  • Tim McElwain
    Tim McElwain Member Posts: 4,596
    Both RI and Mass allow the use of stainless steel plugs. They want the PVC threaded and RTV sealant used with the plugs. I have a work sheet with a picture just send me an e-mail at [email protected] and I will get it to you.
  • Jason_13
    Jason_13 Member Posts: 304
    You mean a manufacturer does not supply a place to take the tests they require?
  • SWEI
    SWEI Member Posts: 7,356
    Most of the current crop have a test port in the flue fitting/adapter.