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Community and Q&A

Spray Foam Around Waste Line

thegiz | Posted in General Questions on

Hi hope everyone is well. Just had a thought cross my mind and hope I am just over worrying. I just used foam board against concrete in my basement. There is a waste pipe running horizontal and vertical along wall. I sprayed foamed both sides of gap between foam board and pvc plumbing pipe to seal any penetrations. Should I be worried about the sewage pipe bursting before I close up the wall? I thought it was common practice to spray foam around piping but maybe I wasn’t suppose to spray along sides?

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  1. Expert Member
    NICK KEENAN | | #1

    Are you worried about the pipe freezing and bursting because it is insulated from the inside but not against the outside? Drain pipes shouldn't ever have standing water in them so they shouldn't be at risk of bursting if they freeze. Areas below the frost line shouldn't freeze either.

  2. user-5946022 | | #2

    Are you worried that as the foam cures, it will expand and put so much pressure on the pipe that it will burst? Or worried about something else?

  3. thegiz | | #3

    Worried about exactly what you said, I think it would have happened by now though

  4. Expert Member
    BILL WICHERS | | #4

    Foam won't cause a pipe to burst. As previously mentioned, sewer pipes very rarely freeze -- natural bacterial action in sewage actually creates heat -- just like a compost pile -- which is one of the reasons for this.

    Spray foam won't exert enough pressure in this application to cause a pipe to burst. The spray foam will just ooze out around the pipe as it expands, with only minimal pressure on the pipe. I've used housewrap before (and off-brand housewrap at that!) as a "barrier" to contain spray foam before and even that works just fine. Once the foam cures, there really isn't any ongoing pressure exerted on the things around it.


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