(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 2 of 2

Thread: Bath fan issue

  1. #1
    DIY Junior Member Newoldhouse's Avatar
    Join Date
    Nov 2013
    New Jersey

    Default Bath fan issue

    Just bought a house and this is my first winter in it. Noticed that all the plumbing vents (two bathrooms and kitchen )are tied into one 2" vent. So my first question is:is that ok to have all in one vent out the roof?
    The real issue I notice right now is that I have I big backdraft out of my one bathroom fan-the only one connected to the multi vent 2" pipe. This makes the master bath ice cold. The other is a plain 4" flex connected to a dryer type exhaust into the attic which has no draft issue (I know , I'll fix that after all the other major issues get fixed). The drafty fan is piped with 2" PVC starting at the fan and very hard to get to. Is the draft due to the undersized 2" pipe? Any suggestions on how to stop it? Should I add roof vents for both baths?

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    First, 2" pvc is probably too small for a bathroom vent and when on, would be inadequate to move much air. Second, joining the exhaust from two different fans rarely works with separate motors (i.e., not designed for it). Third, it sounds like the one vent does not have a damper to stop air flow, either back from the roof, or when the other fan runs.

    So, without having the specs, you'd want to increase the duct size. Dryer vent isn't the best thing, partly because it isn't insulated, and partly because all of the folds slow the air down, and will trap condensation. Solid ducts work better to minimize friction, and maximize flow.

    Ideally, if you wanted to maintain just one roof penetration, you'd switch to something like the FanTec remote motor, and in the bathroom(s), it would just be an inlet grill. This would be quiet, and is designed to work with multiple inlets.

    You need to figure out why the damper in the cold bathroom doesn't work - free it up, or add one, if it was removed, as a work around until you can fix it right. You could also add a second penetration, either through the roof, or maybe a gable end, or maybe even move it to a through-the-wall vent.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

Similar Threads

  1. Adding Master Bath on shared wall with another upstairs bath
    By TommyTwix07 in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 6
    Last Post: 06-10-2013, 01:01 PM
  2. Bath Overflow drain Gasket issue
    By jestructure in forum Shower & bathtub Forum & Blog
    Replies: 1
    Last Post: 01-07-2013, 09:32 AM
  3. Bath/Shower Valve Not Turning Off Bath Water
    By tricky in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 13
    Last Post: 12-15-2007, 08:41 PM
  4. Bath-tub tile issue
    By Lisa Cassells in forum Remodel Forum & Blog
    Replies: 3
    Last Post: 12-13-2006, 07:44 AM
  5. ASSE 1016/1017 issue with bath hot water
    By dhoerl in forum Shower & bathtub Forum & Blog
    Replies: 1
    Last Post: 12-01-2006, 05:53 PM

Tags for this Thread


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts