In article , Chris Green
writes
Harry Bloomfield, Esq. wrote:
R D S pretended :
Having had no bother and it being zero and under recently around
these parts
i'm wondering at what sort of temperature you'd actually get freezing?

Any temperature sub-zero is cold enough, but it also depends on how
long it it below zero.

However MDPE (black or blue) seems to be quite OK when frozen, we have
quite a bit of exposed MDPE pipe outside and it has been frozen and
thawed quite a few times over the years with no apparent ill effects.
(It feeds a couple of horse waterers so temporary blockage doesn't
matter)

The important point is that water expands as it freezes and exerts
considerable force whilst doing so. MDPE pipe is flexible and
accommodates this, copper does not and splits or maybe forces open a
compression joint. Of course you don't know about this until the water
thaws.

--
bert