On 13/11/17 17:45, Scott wrote:
We have a cold water storage tank in the loft, which is not properly
lagged at the moment. My neighbour is convinced there is risk of
flooding of the water freezes then thaws. The tank is made of plastic
(PVC?) not lead. The lid is loose, leaving plenty of space for
expansion. To my mind, freezing would be an inconvenience but no risk
to the integrity of the tank.

However, she also mentioned the inlet and outlet pipes. Could they
freeze and present a risk? Anyone venture an opinion?


Yup

In a cold snap the 80s, we had the water in an unlagged heating
expansion tank freeze, which proceeded to travel and freeze water in the
lagged pipes supplying it, moving apart a not very well made olive
compression joint and flooding the entire 3-bedroom house top to bottom
with 8 hours of unleashed mains water...

It was nightmare clean up, that one. All wallpaper removed and
dehumidifiers running 24/7 for a week ;-(

Lag the tank.

--
Adrian C