Back in the early nineties when a student in Norwich the toilet water froze one winter.
One year, we had hired a cottage just outside Aviemore over Xmas/NY for winter climbing and it was so cold the drains froze and you couldn’t empty the bath!
Mind you, it was exceptionally cold that year, Steal Waterfall, in Glen Nevis, froze solid and night time temp was below -25C.