The message
from "Phil L" contains these words:

Yes, it's the 'long before it freezes' which needs understanding... once it
has expanded enough to freeze solid, excess water has been pushed out
through the open tap.

Not so, or ice would not float. Water expands by a significant amount as
it turns to ice.

It can only burst the pipe if it has nowhere else to go! - if there is an
outlet it will go through this (the tap)....to suggest that the tap is
colder than the pipework is false, the copper is less than a millimetre
thick while the brass is up to 10 mm, ergo the pipewater will freeze first,
pushing the rest of the water towards the outlet.

Nonsense - while it isn't colder, the tap is bulkier, so can drain heat
more efficiently from the copper and the water, whereas the thin copper
of the pipe has to give up heat to the water and to the surrounding air.

Air is not a good conductor, nor does it have a high energy potential.

However, leaving the tap open will certainly lessen the liklihood of a
burst, especially if the freezing is very slow. Ice at or near
freezing-point melts readily when under pressure, resulting in a certain
amount of it being pushed through the tap as ice, and once
unconstricted, the fluid fraction immediately freezes, making it appear
as if the ice has been pushed out as a lump.

--
Rusty
Open the creaking gate to make a horrid.squeak, then lower the foobar.
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