hot water pipe frozen

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the hot water pipe froze last night. we had something like -25C.
first of all, why would the *hot* water pipe freeze and not the cold one? they are completely paralel
second, it's not the first time we've had cold weather, it's usually -20 or so, and it's been colder than -25 before. why not freeze before? why now?
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It's probable you use the cold water more often, so the flow in the cold pipe kept it from freezing.

It's not just the temp, it's also the duration.
Joe F.
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another question: if the pipe freezes, does it automatically crack? it's copper
and since this morning, when I open the cold water in the beginning I see a bit of brown stuff coming out. the faucet is a mixer type thing (one handle for both hot and cold) can that be related to the hot water pipe that's frozen?
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It is also that previously hot water has the air driven out of it, so if previously hot and cold water at the same temperature are cooled at the same time, the previously hot water may freeze first.

Copper may stretch (bulge) instead of crack, but that work hardens it (more brittle), so after some number of freeze cycles, it will reach a point where it splits.

Stretching the pipe loosened deposits (minerals or whatever) on the inside of pipes. Or if on city water and they had a main break, higher than normal velocity during the break or when reopened after repair, can knock loose iron or other deposits.
--
David Efflandt - All spam ignored http://www.de-srv.com /

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No. Copper...or any container...will only crack if it is a seal container...and if the force of the freezing water is greater than the strength of the container.

Maybe.
Have a nice week...
Trent
If the cheese isn't yours...its Nacho cheese, man!
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If the ice expands and has no where to go it will tear apart almost anything. Had a case where water froze in an 1/8 in. dia. stainless steel tube. A small section of the tube, about 3/4 in., expanded like a sausage until it tore along it's length. The tensile strength of the tube was 20,000 psi. The result was a fuel leak and puddle at the back of an airplane and could have blown it up if someone didn't notice the dripping on the tarmac. MLD
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Adjustable temperature control feature contained in a RedyTemp can stop pipes from freezing. www.RedyTemp.com

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I would look for a place where cold air might be blowing into the area where the pipe is. It's possible that a small crack has widened through the years and is blowing right on the hot water pipe.
j j wrote:

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There is less oxygen in hot water and it freezes faster. The hot water gets used less often than the cold water and hence sits still in the pipes longer allowing it to freeze where the cold water that is moving more doesn't freeze. Des

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Brought back some memories. Some years ago, maybe 1988, I had a rented store. I had baseboard electric, and you can only begin to guess how expensive that is.
One day I noticed that one store room was warmer than I thought it oughta be, and somehow the heat was on, but low. I turned off the heat, and figured I saved a bunch of money.
Next morning the one pipe was frozen. If memory serves, it was the hot. Can't explain that. I pushed up the ceiling tiles, and after quite a while I did find the frozen spot. The building had used to be a one bay service garage. Along the right side of the building there was a window I'd never paid any attention to that. It was over the ceiling tiles. And it froze right next to the window.
I ran an extension cord, and thawed it with a hair dryer, adn very glad to have that thawed, without any split or leak. I crumpled a bunch of news paper to pack in the window.
The other frozen pipe experience that comes to mind was a customer in a rural farm house. Weather was about 5F, and blowing cold. Really totaly bitter weather. The water heater was fuel oil fired. The pipe came off the W.H. and ran horizontal right across the back of an old slop sink (laundry tray). Right behind that was a double hung window. The sash was loose, and there was bout 3/8 inch crack between the sash adn the top part.
Fortunately, I was able to thaw that pipe witht he heat from my hands. I did have a torch, but it was up a flight of stairs, and out a long walk to the truck. I took some zip screws (got a bottle of th ose in my tool box like most heating guys) and secured t hat sash quite a bit. That couple screws to tighten the window prevented any more refreezes.
the old counsell still works. Leave a faucet dripping at the farthest part of the house.
--

Christopher A. Young
Jesus: The Reason for the Season
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How hot were the water pipes when they froze? If they were over 32 degrees F, you may want to call Ripleys..
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j j wrote:

Try this experiment, Place two ice tray in the freezer, one filled with hot water, one cold. The hotter one will freeze before the colder one. The reason is that, the higher the temperature different between two surfaces (temperature gradient), the faster the heat flow. pac

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So when the hot tray gets down to the same temperature as the cool tray was, how is it cooling faster?
There is some logic about dissolved gases in the water theory, but I am not at all sure that is valid (or not sure it is not valid). On the other hand the location of the hot water pipe to the source of cold air may well be the problem along with the idea that we generally use the hot water less often. By the coldest part of the day (just before dawn) most hot water pipes have not been used all night and are at "room" temperature. Cold water pipes may well have been used over the night.
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Joseph E. Meehan

26 + 6 = 1 It's Irish Math
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It's an air flow thing. Hot or warm air rises, so in an environment where the temperature is consistent the air about the hot water pipe is heated and rises. This pulls the colder air under the pipe up, where it is warmed by the pipe, etc. The cold air moving upwards cools the pipe causing it to freeze faster than the one with the cold water.
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And once the pipe and the hot water in it reach the same temperature as the cold water pipe was, what keeps the air moving any different than it does around the cold water pipe?
It reminds me of those who say the traffic is so bad during rush hour that if they start 15 minutes later they will get to work sooner (not just take less time to drive, but save over 15 minutes). Of cause this would mean they would have to pass their other self somewhere along the line. ;-)
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Joseph E. Meehan

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Joseph Meehan wrote:

Because the hot pipe will reach the same temp. as the cold one on the bottom were the cold pipe is uniformly the same temp The cold one with dissolved gases and dissolved hardness may freeze at a lower temp (supercooling ) the hot one left the dissolved gas and hardness in your water heater and why you should flush your tank your right the cold pipes are used more and the hot pipes even if ran along side maybe toward the cold air

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Why? If both are cooling why does the hot water pipe cool unevenly and the cold water pipe cool evenly?

That is not "supercooling", but it may be the case. However I would like to see the figures for the different freezing temperatures for water with typical amounts of dissolved gases and hardness vs. those same figures for those for water with typical disolved gases hardness.

--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math
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Joseph Meehan wrote:

Ahemmm...., let me try to get out of this one :-)
But seriously, what make this problem interesting is that, the water temperature is not homogeneous. This mean, the hot water is never cool down to the same temperature as the cold water "homogeneiously".
The outermost layer of the hot water cool faster than the inner layers (assuming the atmospheric temperature is constant.) The temperature difference at the outermost layer, i.e. the surface, of the layer touching the pipe, is largest and hence heat flow out (to the pipe or air) fastest. As the result, the outermost layer would cool faster than inside layers. This will create temperature gradient between different layers in the hot water body. If the air is very cold, the outer most layer may be frozen while the inner core is still warm. This effect is not as prominent if the watrer temperature is not very hot, since temperature gradient is smaller and the heat flow at each layer is slower than the hot water case.
I guess there are more than one causes for this hot vs cold water frozen effect. pac

I remember reading abouyt this. When the temperature is lowered, the gas
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True, but it will never cool down fast enough to pass the cold water to start with.
See my example of leaving later to avoid the rush hour traffic to get to work sooner than you would if you left earlier. To do so you would end up passing yourself. Just as the hot-cold would have to pass itself when it had cooled the boundary layer to equal the boundary layer of the cold water and then continue to transfer more heat out of the pipe than the cool water would.
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Joseph E. Meehan

26 + 6 = 1 It's Irish Math
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time travel- beam me up. I still say his toilet leaks
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