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  1. #1
    Join Date
    Jan 2014
    Posts
    3

    Default frozen plumbing waste stack

    We're in Minnesota and have had a very cold December. This is our first winter in this house. The house was a foreclosure property and we rehab'd it for our residence.

    My plumbing waste stack has frozen closed. It did the same thing a couple weeks ago and we had a plumber go up and remove the ice block and snake the vent pipe - he said there were no obstructions in the pipe. Prior to his visit I did insulate the 12-16" of pipe that was showing in the attic space. The vent pipe runs up the west wall of the house, which at that part is about 2.5 stories tall.

    Since I don't want to hire a plumber every 2 weeks to remove the ice cap on the stack and don't want to go up 2.5 stories on a ladder, does anyone have any suggestions on how to prevent this?

    I've read heat tape can be used but it's a fire hazard, plus I'd then have extension cords running on the outside of the house (which I really don't want). Other suggestions on the web include insulating the pipe in the attic, which I've already done.

    Hoping for some great ideas. Thanks.

  2. #2
    Join Date
    Sep 2012
    Location
    Boston
    Posts
    993

    Default Re: frozen plumbing waste stack

    call an electrician and have him install heating wire. he can install it so that it's on a timer in an accessible location for you. every once in a while when you think it's getting blocked you can turn the heat on for an hour to clear it up.

    a second option would be to put a vent lid on top of the stack so that snow can't collect there but air can still enter.

  3. #3
    Join Date
    Jan 2008
    Posts
    1,905

    Default Re: frozen plumbing waste stack

    What size pipe is the vent at the top? A larger pipe would take more ice to block it. I'm not sure, but perhaps draining a sink full of hot water might get enough heat up there to clear ice. There would be a small amount of leaked heat in the attic coming from the house so I'd also recommend that it not be insulated in the attic- there's absolutely nothing to be gained by that insulation. Ask around to see if any neighbors have the same problem and if they do then maybe they have a fix figured out.

    Phil

  4. #4
    Join Date
    Jan 2014
    Posts
    3

    Default Re: frozen plumbing waste stack

    Quote Originally Posted by Mastercarpentry View Post
    What size pipe is the vent at the top? A larger pipe would take more ice to block it. I'm not sure, but perhaps draining a sink full of hot water might get enough heat up there to clear ice. There would be a small amount of leaked heat in the attic coming from the house so I'd also recommend that it not be insulated in the attic- there's absolutely nothing to be gained by that insulation. Ask around to see if any neighbors have the same problem and if they do then maybe they have a fix figured out.

    Phil
    The PVC going through the attic looks to be maybe 2-1/2", but on the roof is a metal stack with flange - the kind like you'd get from a home improvement store. I'll have to check with the neighbors, especially the houses of teh same vintage (built in 1985). We tried the hot water idea and that didn't work.

    Thanks for your suggestions.

  5. #5
    Join Date
    Jan 2014
    Posts
    3

    Default Re: frozen plumbing waste stack

    Quote Originally Posted by MLB Construction View Post
    call an electrician and have him install heating wire. he can install it so that it's on a timer in an accessible location for you. every once in a while when you think it's getting blocked you can turn the heat on for an hour to clear it up.

    a second option would be to put a vent lid on top of the stack so that snow can't collect there but air can still enter.
    I'll need to get an estimate from the electrician. My main concern is how they'd get power up there. I did wonder if I could connect a solar panel to the heat tape. The wattage output is low so not much of a fire hazard, but I don't know if there's enough power to even get the heat tape warm.

    Snow doesn't seem to be the issue but I'll watch for that. Thanks for your help.

  6. #6
    Join Date
    Dec 2013
    Location
    Montreal Canada
    Posts
    183

    Default Re: frozen plumbing waste stack

    it is very important that the plumbing stack run inside the house not on an outside wall.that being said if the stack is run on an outside wall insulate between the stack and the outside wall but leave no insulation between the stack and the inside wall.the heat from the house can keep the stack somewhat warm also check all toilets if they run on. what can happen if a toilet runs even so slightly water will run down the stack and freeze. the same thing happens in Canada all the time.

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