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Sealing plumbing vent pipe on roof and air-sealing in attic

Post in 'DIY and General non-hearth advice' started by joefrompa, Apr 16, 2011.

  1. joefrompa

    joefrompa New Member

    Joined:
    Sep 7, 2010
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    SE PA
    Hi all,

    Went up into my attic today looking for a leak and found out my vent pipe (or poop pipe as I've heard it)has a slight leak and is running down from my roof, through my attic, and down through a roughly 12x8" open hole down into my second floor (and I imagine down to the basement or near).

    There's insulation stuffed in the hole, but it's obviously not air-sealing - the insulation was solidly dirty.

    My thought was to take a sheet of thick foam insulation up there, cut it to size and then caulk/foam seal it around the pipe and surrounding hole - then pile insulation on top?

    Also, on the roof, to repair a leaky vent pipe collar - can I simply put a new rubber collar on top of the old one and seal it against the pipe?

    Joe

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  2. fishingpol

    fishingpol Minister of Fire

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    Putting a new pipe boot over the old one is just south of Hackville. It would not sit flush and just cause problems. Carefully remove the old one and replace it. Use care lifting any shingles around it and reseal them down when done. If it was a small leak at the rubber boot, you probably could get away with a sealant, but why not just replace it if you are up there.
  3. woodsmaster

    woodsmaster Minister of Fire

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    I agree replacing the whole flashing is your best option. You can use a flat bar to break the tar seal and pull any nails you need to. If you've never did any roofing or don't want to get on the roof I would think you could
    find a roofer to replace it for around $100.00 It would probably take less than an hour and the pipe flashing cost sround $8.00 DON'T TAR IT UP THEN WHEN IT LEAKS AGAIN CALL THE ROOFER. That makes it much harder to change. And it will probably leak again later if you tar it.
  4. CJ-SR4ever

    CJ-SR4ever New Member

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    New Hampshire
    I had the same thing happen at my house. The water leaked in around the pipe and soaked the ceiling in my kitchen. I ended up sealing around the pipe with silicone and it did the trick.
  5. wahoowad

    wahoowad Minister of Fire

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    Virginia
    Go to Lowes and get:

    1) a tube of roofing sealant (black tar like stuff) that fits a caulk gun;
    2) correct size slip-on pipe boot

    Turn the new pipe boot upside down and squirt a heavy double bead of the sealant over the flat bottom. Turn it right side up and slide it down over the pipe. Push it down solidly. Put ladder and tools away as you are done.
  6. Highbeam

    Highbeam Minister of Fire

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    base of Mt. Rainier on the wet side, WA
    Another hack.

    To properly replace the roof jack, that boot, on a comp roof you do not use tar or any other sealant. You properly shingle the boot in so that water rolls off of the boot and down the roof. When you're done, no nails will be visible.

    If you don't know how to install a roof jack then hire a roofer. These slow leaks can cause rot and mildew, damage that is much costlier to repair than if you had just done it right from the start.
  7. woodsmaster

    woodsmaster Minister of Fire

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    That is as hillbilly as it gets. Just asking for trouble down the road, and a harder fix.
  8. woodsmaster

    woodsmaster Minister of Fire

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    + 1 thats why they call them no caulk roof flashing.
  9. benjamin

    benjamin Minister of Fire

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    A hack or a jack?

    Around here a roof jack is the bracket that holds your planks on a steep roof.

    To the original post, YES on both questions.

    Plug that hole (and all of his friends) ASAP, you're done with the heating season but all summer long that hot attic air is going to be pulled into your house by the cool air escaping out your basement.

    And yes, you can take another rubber boot, pull it off of the rest of the flashing and slide it down right on top of the old flashing, no sealant (or guilt) needed. Some silicone would work just as well without the new flashing. This is assuming you have an existing steel or plastic flashing with the rubber ring in the middle and not an old lead flashing on cast iron pipe. Don't make a small leak in a high spot into something worse by tearing into the shingles that are probably on their last legs already.
  10. semipro

    semipro Minister of Fire

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