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Thread: Venting problem in my parent's house: Help

  1. #1

    Default Venting problem in my parent's house: Help

    Went home for the holidays and stumbled upon a plumbing problem at my parents 70's single story ranch house. It started when my mom showed me a leak in their bathroom ceiling coming through the drywall. I climbed into the unheated crawlspace above it and found that the main vent stack vented right into the crawlspace (does not penetrate the roof). Someone had attached a flexible dryer vent to it that led to the eave. This had a low point right above their bathroom in which water must have condensed and a hole developed leading to soaked insulation and a ruined ceiling.

    So, I want to fix this. Seems to me I have three possibilites (in order of hardness).

    1) Remove the dryer venting and let the vent leave it venting into the crawlspace. The roof has a continous ridge vent and vents along the eaves, so it is pretty well ventilated.

    2) Make a new vent that leads to the eave out of PVC pipe. This would attach to the 4" copper of the existing vent pipe via a no-hub or something. This piping would run basically horizontal and/or slight downhill (problem?).

    3) Continue the vent through the roof. Since they have a hand split cedar shake roof, this would be the hardest option.

    Any thoughts? I'm here on vacation and hope to leave soon (i.e. the easier the better).

    Thanks, and Happy Holidays!

  2. #2
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    Although not my area of strong expertise, I think I can say with confidence that terminating the stack inside the attic crawl space, either straight up or routed "towards the eaves" with rigid or flexible duct is absolutely unacceptable. Besides the condensation and leaking issue you now have, you have the distinct possibility of sewer gases up there. The main stack vent needs to terminate about 2 feet above the roof line. Probably need the help of a roofer to put this through, flash it, and get the shingle situation patched in.

    How about some further comments from the "heavy guns" on this site!

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    I'm not a pro...so take that in stride. You need to get the vent outside. It doesn't have to go straight up, but should never angle down. To keep the height minimum, you could angle it up closer to the roof peak inside so that when you do penetrate the roof your 2' above the peak doesn't result in a flagpole. Other than potentially being slippery, cutting a hole in a shake roof should be easier than some other types. The flashings for these things are fairly easy, too. You'll want to brace the pipe a little, but not a big deal with the hangers available.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4

    Default Thanks

    Thanks for your advice. Unfortunately, my parents live in Clinton, NY in heart of the snow belt, so doing work on their roof is pretty hard right now. Because of your advice, they will be calling a roofer and having him patch in a vent though the roof ASAP (maybe not til Spring?). In the meantime, I installed a new semi-rigid metal dryer vent back to the eave (as it had been for the last 30 years until the old one sprung a leak) and secured it so it slopes downhill. This allowed me to feel fairly confident in going ahead and replacing their wet insulation and drywall. I will make sure that they follow through and get the vent fixed. Thanks again (and I'm not ignoring your advice by reinstalling the dryer vent, its just a temp solution).


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