It's an urban myth that hot water will freeze faster than cold
water. Supposedly if you take a cup of hot water and a cup of cold
water and place them in a freezer, the hot water will freeze faster.
But it's not true. The amount of water that is lost from evaporation
doesn't make enough difference. The cold water freezes first.
In a plumbing system, either pipe could freeze first depending on when
it was last run, differences in exposure, etc.
The description I read was most likely pointed to from here, or maybe
was on a physics newsgroup, and was about inside a pipe, so
evaporation was not a factor.
It was probably years ago when I had a different hard drive, so I
won't be able to find it in my computer. It had something to do with
something that changed when the water was heated, that made it easier
for it to freeze later. I haven't foundd reference to that in the
posts below, but I have barely read them.
Here are some webpages on the subject
Straight dope says no but then says yes under some conditions, and
then relies on evaportation to explain those cases.
I have barely read these pages yet, but
I googled on hot water freezes faster than cold if you wnat to
look for more. I'll read them tonight but I wanted to post befroe
this thread rolls off the top of the screen and falls behind the desk.
Actually, absolutely not true. You need to cool the water first before
it can freeze.
The "half truth" is based on the fact that water looses more heat ,
faster, when it is hot than when it is cold - but the hot water still
takes longer to reach freezing than the cold water does. Simple
You poor suckers that are not used to the cold, and are not prepared
for it, with houses not built to handle it, are sure having a time of
it. Up here it's been about -5F just about every night the last week.
If the water is flowing it has to be pretty darn cold to freeze. When
water mains are being repaired and surface piping is used up here in
the cold, a tap is left running to keep the water flowing and the
pipes don't freeze unless it's down close to zero. If the water is
turned off, the pipes freeze in a jiffy.
Ice in the pump can split the pump quite easily. Often as it thaws.
Minimum density of water is at +4C - so that's where it takes up the
most space. If both ends are plugged with ice and the middle thaws, it
CAN split things that survived the freezing without damage.
On Sat, 09 Jan 2010 16:17:53 -0800, email@example.com wrote:
Urgh. At least it was still frozen when you found it. I had one a couple
of years ago where the water left in the pump/drain had frozen
overnight, expanded and pushed the drain pipe off. Then it had thawed
by morning, so first load dumped water out all over the floor...
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