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Hot water pipes burst first?

Zman
Zman Member Posts: 7,569
I know there was a conversation a while back that touched on this but a recent experience got me thinking again...

I have 2 identical copper domestic water pipes (hot and cold) that are strapped to the wall of my garage with van hangers. Both pipes have a spring check at the bottom, about 3' of pipe and then a closed ball valve before they go to my pressure washer.

Last night, the garage door was left open with an outdoor temp of 3 degrees. Needless to say, the pipes froze. The hot water pipe split wide open and the cold was not even deformed. Keep in mind, neither pipe had been used in weeks, so the water in the pipe would have been the same temp at the beginning of the event.

I have always noticed that hot water pipes sustain more damage in freezeups than cold, but I have never had such a perfectly controlled (accidental) example.

So here is the theory. The cold water picks up dissolved gasses in treatment and transportation. When the water is heated at the house, some of the dissolved gasses come out of solution. The difference in gas content changes the amount the water expands? The gasses act as a cushion?

Thoughts?
"If you can't explain it simply, you don't understand it well enough"
Albert Einstein
rick in Alaska

Comments

  • luketheplumber
    luketheplumber Member Posts: 149
    I think that I heard about hot water cooling faster that cold water before. I'll look this phenomenon up.
    I just earned my GED and am looking for a apprenticeship with one of these steam gurus on this site!
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,289
    Hi @Zman , lots to consider. I know dissolved gasses are supposed to come out of solution, but if it's essentially a closed system, where will those gasses go? Also, dissolved gas is no longer in a compressible form, is it? It isn't little bubbles that can be compressed. So, I'm wondering if it's something more mechanical, like a spring check that leaks just enough to prevent pressure from building in the freezing line. Of course ice could burst the pipe by itself... Maybe replace the lines with insulated PEX?? B) I'll be curious to see what others come up with. Sounds like a research project!

    Yours, Larry
  • Zman
    Zman Member Posts: 7,569

    I think that I heard about hot water cooling faster that cold water before. I'll look this phenomenon up.

    That's the direction I was headed until I saw this. The temp of the water in both pipes was the same because they had not been used recently. The spring checks at the bottom should have negated thermal siphon. The only difference I can see is that hot water was previously heated. Both pipes where originally the same stick.

    @Larry Weingarten
    I thought that might be the thin spot in my theory. :D It could also be chance or a valve that leaks a little....
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • jumper
    jumper Member Posts: 2,246
    Here's a theory. Hot water pipes experience wider temperature swings. The copper either gets a bit weaker or more brittle? Next experiment is to freeze both hard copper and soft copper.
  • mattmia2
    mattmia2 Member Posts: 9,632
    My guess would be that it simply was closer to the cold. The dissolved gas when it comes out of solution may collect somewhere and not be distributed to that branch and some dissolved mineral may be removed when you heat it, but the difference in freezing point wouldn't be significant because there is so little dissolved minerals relatively speaking.
    ethicalpaul
  • luketheplumber
    luketheplumber Member Posts: 149
    It's called the Mpemba Effect. You may be right about the gasses @Zman
    I just earned my GED and am looking for a apprenticeship with one of these steam gurus on this site!
    Zman
  • Zman
    Zman Member Posts: 7,569
    jumper said:

    Here's a theory. Hot water pipes experience wider temperature swings. The copper either gets a bit weaker or more brittle? Next experiment is to freeze both hard copper and soft copper.

    I like where you are headed with this but...
    I installed the pipes about 8 months ago. I have only put a few hundred gallons of 130 degree water through them.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • mattmia2
    mattmia2 Member Posts: 9,632
    And copper pipe is hard drawn. It is annealed where you solder it, but it is more or less already hardened.
  • psb75
    psb75 Member Posts: 833
    When water gets heated oxygen and other gasses leave and come out of solution. The water then becomes more dense i.e. becoming closer to its solid state... that being ICE. So if you have two pipes sitting in a garage, one with cold water (never having been heated and full of gasses), and the other with water that was heated (with gasses having been driven off)....when chilled, which do you think will freeze FIRST--and BURST? Another unfortunate fact in plumbing: frozen water is BIGGER than liquid water.
    Now...you might also ask yourself this perplexing question: how come ICE--which is water in its SOLID state, FLOATS on top of water- which is in its liquid state? Shouldn't a SOLID be residing at the bottom of the liquid?
    There would be no life on earth if this were the case!
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    edited January 2021
    Original discussion:

    https://forum.heatinghelp.com/discussion/180471/which-freezes-first#latest

    I believe that ice will become less dense than water, as it expands at the freezing temperature point, and so floats.
    I like the gas bubble theory where the bubbles will act as miniature expansion tanks. It’s not so much a question of which freezes first, but rather which expands more as it freezes.—NBC
    Zman
  • Zman
    Zman Member Posts: 7,569
    edited January 2021
    psb75 said:


    Now...you might also ask yourself this perplexing question: how come ICE--which is water in its SOLID state, FLOATS on top of water- which is in its liquid state? Shouldn't a SOLID be residing at the bottom of the liquid?
    There would be no life on earth if this were the case!

    The when the water freezes it expands, it does not gain any measurable weight in the process. The ice is less dense than the water and therefore it floats.

    Also, wood floats and ducks float, so if it weighs more than a duck, it must be a witch. :o
    Sorry, I can talk about buoyancy without a little Monty Python...
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    ethicalpaul