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Buried water pipes freeze-has been cold-the sun comes out

  1. Feb 26, 2015 #1
    Hi: I am a EE, but I have a question that I have searched for on the Internet and not found an answer. Contractors tell me that when it has been cold for several days and the sun comes out, that buried water lines that have not frozen all winter will suddenly freeze solid. It must be a real phenomenon, because they all have the same description: "The heat drives the cold down". I would like to know if anyone has a reason that is based on the laws of physics.

    I have asked on another forum where there are some smart guys of various technical backgrounds, but they don't believe it. Most of them also don't believe that warm water can freeze before cold water, even after I posted to link that claims to verify it (known as the Mpemba effect".


    Any ideas?
  2. jcsd
  3. Feb 26, 2015 #2


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    Staff: Mentor

    Welcome to PF!

    No, the heat does not drive the cold down. What probably happens is that the cold continues to travel down for a little while after the sun comes out.
  4. Feb 26, 2015 #3


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    Yes. You shouldn't expect to get valid scientific theories from a website called businessinsider.com. :frown:

    It can take several days for the temperature below ground to change in response to changes in the ambient temperature. After all, earth does have some insulating effect. It was probably coincidental that the buried water pipes froze just as the weather turned sunny. :wink:
  5. Feb 26, 2015 #4
    Maybe you would like this reference better: http://arxiv.org/abs/1310.6514

    Also, it wasn't just a one-time occurrence; it was common knowledge among contractors, as was the other effect referenced above.
  6. Feb 26, 2015 #5
    What is the symptom of the "pipes freezing solid." Is it (a) that the pipes burst or (b) that no water flows through them any more?

  7. Feb 26, 2015 #6


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    That's a sperate issue to the OP. If the pipes froze earlier in the winter after a warmer summer it might apply. Warming the earth above a pipe will raise the temperature of that pipe, there's no two ways about it.
    I'd guess urban myth along with coincidence. Unless flow rate has some correlation to the sun in which case flow would drop enough for the pipe to freeze..
  8. Feb 26, 2015 #7
    You have to explain what pipes the contractors are talking about. Common practice would be to bury the pipes below the frost line, where the soil never freezes. A cold snap will drive the frost line farther down, sometimes overlapping the pipes.
  9. Feb 26, 2015 #8
    I'm not sure.
  10. Feb 27, 2015 #9


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    Big red flag.
    Properly backfilled, this is great. "Common practice of 'Industry standards' " is not so great. Snow melt soaking into loose backfill and freezing raises thermal conductivity of "soil" over pipes and you ARE in trouble.
  11. Feb 27, 2015 #10
    I was a little hesitant to put it down that way, which is why I asked the question about the contractors and their pipes, but I wanted to get the frost line out there. Loose granular fill, instead of a more clayish fill might be standard in that area. With salted roads, and that leaking down spells more trouble.
  12. Feb 28, 2015 #11


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    There is also the complexity that when things start to warm, pipes on the surface thaw and water starts to flow again. A layer of ice on the inside of a pipe may break away in warming weather and become mobile. That mobile ice may move into places where it can plug the flow for some time.
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