PVC Pipe Roof Vent Leak Onto Ceiling

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by DMD1991, Aug 30, 2006.

  1. DMD1991

    DMD1991 New Member

    Aug 30, 2006
    I noticed some water stains on the ceiling of my bathroom - I went up to our attic and saw that the stains were directly below the PVC pipe roof vent tubes...I put a tray below the "elbow" of the tube and noticed that indeed after rain storms, water did accumulate. I couldn't find any noticeable cracks in the tube (house is only 10 years old) but did feel wetness on the bottom of the elbow...I am at a loss as to what to do? Should I replace the "elbow" or provide some sealant around the bottom of the "elbow" and all PVC tube connections?

    I greatly appreciate any help....Thx
  2. prashster

    prashster New Member

    Dec 7, 2005
    It's unlikely it's a bad joint. Even a dry-fitted vent run probably won't leak; there isn't enough pressure or volume of water in there (even in a storm). My guess is the leak is coming from the flashing around the vent pipe exit in the roof - not from a defective coupling. The water might be running down the outside of the pipe and dripping off the el. Can you gingerly use a ladder or an extension pole and rag to detect moisture on the underside of the hole?

    If the problem is the flashing, then you need to fix it from the roof (read, HAVE A PRO DO IT; DON'T GO SHEMANGLING UP ON THE ROOF YRSELF). If you just caulk the underside of the exit hole attc-side, then water can enter the roof sheathing from above and potentially rot yr roof.

    If the problem is a leaky el, then the right thing is to cut it out and replace it. However, if it were me, I'd first caulk the seams of the el. and see how that holds up. Since there's no pressure in the vent pipe, caulk (silicone) will probably suffice.
    Last edited: Aug 30, 2006
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  4. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Nov 8, 2005
    Hansville, Washington
    I can tell you from experience :( that a dry-fit joint at a downward-turning ell will leak during a rainstorm. It's really easy to fix, though :) . Odds are slim that it would pass the pressure test, though, so that's probably not your problem, although a poorly fit joint could fail after 10 years of flexing in an attic.

    Having said that, do be certain that the water isn't simply choosing to drip off at the elbow, having come down from somewhere higher. If it just started leaking after 10 years, I'm with prashter -- check the flashing around the vent pipe where it exits the roof.

    I spent some quality time shemangling on the roof yesterday cleaning things up for Ernesto, and glopped a bunch of roof cement on several suspect joints. Cheap insurance.
  5. Master Plumber Mark

    Master Plumber Mark Master Plumber

    Feb 6, 2005
    Sensitivity trainer.. plumber of mens souls
    indianapolis indiana - land of the free, home of
    tar pitch

    just go buy yourself a gallon of black roof tar cement... $5 bucks

    go uop on the roof , (if you are capable) and take the

    tar pitch and a nice --wide putty knife and simply apply a heavy

    and generous amount of that tar all around where the pvc pipe comes out

    through the roof I suggest you smear it on all the exposed flashing and

    make it all black.......

    just seal up over that neopreme with the tar and no one will be

    the wiser from the ground.....unless you make a total mess of it....

    it applies rather well and will harden up ok.....

    good for about 35 years....

    I doubt that the elbow inside the ceiling is leaking

    but if it is you can do the same on a dry day with silicone

    to that elbow without takeing it all apart and messing up

    that seal through the roof....

    good luck and have fun......
  6. DMD1991

    DMD1991 New Member

    Aug 30, 2006
    Thanks to all who responded. I really appreciate your input
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