Why do Freezing Pipes Burst?

Discussion in 'General Plumbing Help' started by Diehard, Jan 22, 2019.

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  1. Jan 22, 2019 #1

    Diehard

    Diehard

    Diehard

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    The following information is included in a document entitled, "Freezing and Bursting Pipes", published by IBHS (Insurance Institute for Business & Home Safety).

    Who writes these things and where do they get their information from?

    "WHY PIPES BURST
    Surprisingly, ice forming in a pipe does not typically cause a break where the ice blockage occurs. It’s not the radial expansion of ice against the wall of the pipe that causes the break. Rather, following a complete ice blockage in a pipe, continued freezing and expansion inside the pipe causes water pressure to increase downstream -- between the ice blockage and a closed faucet at the end. It’s this increase in water pressure that leads to pipe failure. Usually the pipe bursts where little or no ice has formed. Upstream from the ice blockage the water can always retreat back towards its source, so there is no pressure build-up to cause a break. Water has to freeze for ice blockages to occur. Pipes that are adequately protected along their entire length by placement within the building’s insulation, insulation on the pipe itself, or heating, are safe.":confused::eek:
     
  2. Jan 22, 2019 #2

    frodo

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    idiots with out a clue

    water expands slightly as it freezes
    when frozen it expands 9%
    this breaks the pipe
     
  3. Jan 23, 2019 #3

    Diehard

    Diehard

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    Yes...I couldn't believe what I was reading.
    I wrote to them and curious to see if I ever hear back from them.
     
  4. Jan 23, 2019 #4

    fixitron

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    Yes, the water expands when it freezes and the expanded ice is what bursts the pipe. Think about frost heaves.

    What many people do not realize is that insulation does not stop heat loss, but only slows it down. Heat energy always flows from hotter to colder. If relatively warmer (even at 50 degF) water occasionally flows through the pipe, it probably won't freeze. Otherwise, any pipe exposed to below freezing temperatures will eventually freeze, no matter how much insulation is on the pipe, because the heat in the pipe flows from the pipe to its surroundings. In addition, if there is just one spot where a draft from outside can hit a pipe, that is where it will freeze first. A piece of rigid insulation between that pipe and the outside wall will go a long way to preventing that freeze-up.
     
  5. Jan 23, 2019 #5

    CT18

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    I was standing in my neighbors garage with him last winter when his service froze before the meter. Why his is in the garage blows my mind. As we were accessing the situation there was a pop and the line split right in front of use where it was frozen.
     
  6. Jan 23, 2019 #6

    FishScreener

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    Easy way to find out. A two foot piece of copper, with a cap soldered on one end, with the other end open.

    Stand it vertical, and fill it with water.

    Take some dry ice, and starting about six inches from the open top end, work your way downward, freezing the water as you go.

    If they are right, the pipe won’t split where it is frozen, but will burst towards the bottom, as you progressively move the frozen section, and ice plug downward, increasing the water pressure on the still unfrozen water.
     
  7. Jan 24, 2019 #7

    bowserb

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    I thought I remembered this from 6th grade science, but I looked it up to check my memory (I'm 72). Like virtually all materials, water expands when heated and contracts when cooled. However there is an anomaly with water as temperature drops toward freezing. Water volume contracts as it cools, but as it drops below 40F and to 32F, it expands due to crystallization. Once crystalized and frozen, it again acts like expected, as temperature drops below 32. Of course, if the water happens to have been trapped in a pipe as it approaches freezing, bang. Broken pipe. FishScreener's suggested science experiment would be a good one for the classroom, if you're inclined to volunteer. Like so much else these days, not many kids get out of school knowing the water freeze anomaly. That copper pipe demo might be a good teaching tool, especially if you could substitute something transparent for copper.

    Barely related: The weight of liquids is usually expressed in pounds per gallon, at least here in the U.S. But that weight is also specified at 60 degrees F. So water weighs 8.33 pounds per gallon at 60 degrees. I think barometric pressure has some impact but usually not enough to matter. "Specific gravity" of a liquid is generally a ratio of the weight per gallon of the liquid to the weight per gallon of water. Gasoline, for example, has a specific gravity of around .74, depending on the formulation. A liquid with a specific gravity less than 1.0 will float on water. Of course, the temperature comes into play here as well, since gasoline, diesel and other hydrocarbon compounds also expand as they warm, they are typically sold to distributors and dealers by weight when possible. Of course in the case of bulk transfers, that requires that a truck scale be available, although with an official table and thermometer a decent approximation can be made. There is a story about a truck stop on I-20 in Texas, where the diesel and gasoline storage tanks were above ground and painted black. The truck stop purchased its fuel by weight, but of course sold it by volume as measured by the dispensing pumps. Supposedly half the truck stop's fuel sales profit came from fuel expansion, since competition kept the markup low.

    Note. I am not a scientist. I just play one on the Internet.
     
  8. Jan 24, 2019 #8

    chiraldude

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    The statement from the insurance organization is basically correct but I would disagree with the assertion that the burst typically happens far from the pipes that freeze first. Usually a burst happens between 2 90 deg elbows. Ice in a frozen pipe will actually flow (more like slide) inside a straight pipe but not through a bend.
    Radial freezing of a small section will never cause a pipe to burst. As the water freezes, it pushes liquid out of the center of the pipe so pressure is released. This fact is sometimes used when a pipe needs to be serviced but the shutoff valve is not working or not available. Search for "pipe freeze kit" and you will find lots of tools and videos on how to do this.
     
  9. Jan 24, 2019 #9

    frodo

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    It’s this increase in water pressure that leads to pipe failure. Usually the pipe bursts where little or no ice has formed

    the above sentence is the objection i have to the statement from the insurance co.
    I find this to not be the case.
     
  10. Jan 24, 2019 #10

    Diehard

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    I tend to agree, based on my frozen, ruptured heating pipe in my basement loop. The break was exactly where the pipe was subject to the cold air leaking in over the basement door frame.

    Regarding the "pipe freeze kit" info. I saw a lot of videos using it and talking about it, but I didn't come across anything that confirmed that the break TYPICALLY doesn't happen at the point of the expanding ice. Or for that matter anything that caused rupturing of the pipe. Please provide a link, if it exists.

    I did see one video that cautioned not to locate those freeze points too close to an elbow because it's liable to blow it off. Hmmmm
     
  11. Jan 25, 2019 #11

    pasadena_commut

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    Interesting experiment. However you are assuming that the ice in the frozen section is stuck in place and cannot move. That may indeed be the case. On the other hand, the inside of a new copper pipe is very smooth and the pressure of the water at the bottom may just force the plug upward so that the pipe never bursts. Add a 90 degree elbow at the top of the pipe, tilt the pipe so that it can be filled to the top of the elbow, repeat the experiment. That should burst the pipe because the ice will not be able to slide around the bend. Exactly where it bursts I wouldn't predict. It might be in the liquid water section, or the pressure from the ice may cause the elbow junction to fail.
     

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