Franz Heymann wrote:
:: "Phil L" wrote in message
:: . ..
::: Franz Heymann wrote:
::::: "Phil L" wrote in message
::::: . ..
:::::: Sue wrote:
:::::::: ........ how can I protect my outside tap from freezing up?
::::::::
:::::::: Sue
::::::
:::::: Turn the water off at it's supply...draining it is unnecesary
:::::: as any water which remains inside it will expand out of the
:::::: tap if you leave it in the 'on' position.
:::::
::::: That depends on whether it freezes solid at the tap end first.
:::::
::: The water at the tap end will expand though the outlet...unless
::: there's a long pipe (half a metre or more)outside, this will not
::: cause any problems.
::
:: Not if the water freezes solid at the tap end before the water in
:: the rest of the pipe begins to expand as it gets cold.
::
:: It is of the essence to realise that water starts expanding when
:: its temperature drops below 4 deg C, long before it freezes.
::

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.

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.