In article , Phil L
writes
The pipe contains 15 mm of water, encased in a 1 mm copper sheath, the tap
contains 25mm of water encased in a 10mm brass sheath, which is going to
freeze first?

Neither of them contain anything like that amount of water unless either
you have blocked the end of the tap or are keeping it full on. What they
both perhaps contain is a small amount of water coating the sides. And
the tap is open at the end.

The likely scenario is, therefore, that the water will freeze at the
opening of the tap first, and further trickles will run down and freeze
on top in layers until the tap is blocked.

--
Kay
"Do not insult the crocodile until you have crossed the river"