For some reason, the hot water pipes in places I've lived freeze faster than the cold water pipes during a cold snap. This is counter intuitive and the web seems full of controversy on this subject. It has even been given a name -the Mpemba effect.
Because you run the cold water much more frequently so the pipes the cold water is delivered through are much cleaner whereas with hot water not being run as often more sediment and other impurities get deposited in the pipes and the water heater itself.
Water with more undisolved impurities(because disolving something in it will have the opposite effect) freezes at a higher temperature than water that is more pure.
Then you have to combine that with the fact that while the hot water is not running it stays still in the pipe where it is then exposed to the elements and returns to room temperature. So you end up with a pipe full of clean water and a pipe full of dirty water and the clean water has less impurities to act as seeds for ice crystals.
What about the myth that cold water boils faster than hot water? I 'tested' this out with my brother while we were havin a cook-off and the hot water definitely kicked the cold water.
This message has been edited. Last edited by: mod_ivy,
hot water contains more thermal energy and by freezing you are removing that energy. therefore, since the cold water already is closer to the freezing point because of its lower thermal energy it will freeze first.
or
The answer is that it precipitates out solutes.
The solutes are calcium and magnesium bicarbonate, which make most drinking water "hard". When the water is heated, these precipitate out to form the solid scale that "furs" up the inside of a kettle.
Water that has never been heated still contains these solutes. As it freezes, ice crystals form, and the concentration of solutes in the remaining water becomes ever higher up to 50 times as high as normal. This lowers the freezing point of the water, just like salt sprinkled on a road in winter. "The water therefore has to cool further before it freezes"
For some reason, the hot water pipes in places I've lived freeze faster than the cold water pipes during a cold snap.
To be blunt, I don't believe you. I've lived in the snow belt my entire life, and I have only had pipes freeze once - and it was the unheated main. The number of people who've experienced frozen pipes that I know of is in the low single digits, with no bias toward hot or cold - the water standing in a pipe is always cold after a few minutes. So your claim of this as some sort of common occurrence doesn't match reality very well.
I think you just picked a story off a website and personalized it for some reason.
But that aside: as already noted, hot water pipes, especially those made from galvanized steel, tend to clog with minerals much more so than cold water pipes. What you wind up with is a pipe that is much narrower - and which holds much less water - than it's cold-water neighbor. But given the lack of any actual evidence that this bias exists, I'd say this is an explanation of something that never happens.
The so-called "Mbempa Effect" is completely non-existent - it is an artifact of sloppy experimental design and execution, not a real phenomenon.
Forums 