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  1. #1
    Join Date
    May 2009
    Posts
    10

    Confused Leaking furnace exhaust pipe

    I have a PVC furnace exhaust pipe in my attic that is running horizontally for a short bit to get from the service chase to where it penetrates the roof. It is currently dripping water onto the ceiling right by the 90' fitting where it turns to go down the service chase.

    I have a few questions that I hope the experts here can help me with.
    1> should the PVC be glued with regular PVC primer and glue like is normal for sewer drain/vent? (It looks like the installer used black ABS glue)
    2> Should the exhaust vent be installed such that it always has a slope down towards the furnace? (ie. any "horizontal" runs should have a slight slope towards furnace?)
    3> Should the air intake vent also be sloped toward the furnace? (It's next to the exhaust in the chase and come together for a concentric vent penetrating the roof)

    4> I would guess water (rain) will sometimes get into the exhaust and air intake vents. Is there anything I should be concerned about with that? Is that rain water going to normally wind up win the same place as the furnace's condensate?

    5> what else should I be looking for? Obviously some things were not done right by the installers, so now I wonder what else I should check on.

  2. #2
    Join Date
    Mar 2009
    Location
    Chicago Area
    Posts
    29
    you need to call for service, you could try the people who installed but they seem to have done a bad job. Ask around for some referances of good HVAC co in your area

  3. #3
    Join Date
    May 2009
    Posts
    10
    Quote Originally Posted by keekee View Post
    you need to call for service, you could try the people who installed but they seem to have done a bad job. Ask around for some referances of good HVAC co in your area
    I do need to get someone in to fix it - but I also needto be able to talk intelligently to them. And know if what is being done to fix it is the appropriate thing...

    I suspect that the original installers used ABS glue (because I can see it's black) when they should have used PVC glue & primer. But if there's really black PVC glue that's normally used for furnace vents I'll look like an idiot if I track down the original installer and tell them they need to redo all the fittings because they used the wrong glue. (I suspect I actually won't use the original installer, but I haven't decided yet)

  4. #4
    Join Date
    Mar 2007
    Location
    Madison, Wisconsin
    Posts
    2,260
    The primer is probably the purple stuff, it is fine on PVC. Hope they used the right glue. Yes the vents should slope back to the furnace. You are probably seeing condensate dripping from a cracked fitting or one that was not glued correctly. Get the installer back out.
    I r the king of the world!...or at least I get to stand on the roof and look down on the rest of yall

  5. #5
    Join Date
    May 2009
    Posts
    10
    Quote Originally Posted by Wheelbaron View Post
    The primer is probably the purple stuff, it is fine on PVC. Hope they used the right glue. ... Get the installer back out.
    No primer visible - just black (or very dark grey) glue on white PVC.
    I know the purple PVC primer well from doing DWV work for regular plumbing. I've heard someone talk a while back about clear PVC primer (yes clear primer, not glue), but haven't seen that myself. It's quite possible that furnace guys use something I'm not familiar with though.

    I'm not sure I trust the original installer - and it's been a few years, so I'm currently leaning towards getting someone new in.

  6. #6
    Join Date
    Mar 2009
    Location
    Several Miles from Sane
    Posts
    1,471
    There is a "Grey" PVC glue commonly used on Electrical PVC conduit. It is a battleship grey, meaning it's not "Dark Grey". Either way installer should have used primer. I should be obvious where the primer was applied even if it was clear primer.

    Yes there is clear PVC primer. I always tried to use it cause I think the purple primer looks crappy.

    Dumb question, I don't know where you live but was there an inspection of the installation by local authorities ?
    If sense were so common everyone would have it !

    All opinions expressed are my own. Any advice provided is based on personal experience, generally accepted fact or publicly available information. As such, it is worth exactly what you paid for it, not a penny more not a penny less !!

  7. #7
    Join Date
    May 2009
    Posts
    10
    Quote Originally Posted by CCIKelly View Post
    Dumb question, I don't know where you live but was there an inspection of the installation by local authorities ?
    I don't know if there was an inspection or not - but even if there were, I wouldn't be surprised if they didn't bother to crawl up into the attic. How many inspectors have you seen really inspect all of a job thoroughly?

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