Mains water leak under the kitchen sink. Chaffing by the chipboard shelf
over 30 years had eventually punctured the 15mm copper pipe to the cold
tap.
While in there noticed the screw for the electricity supply earth bond
was laying on the shelf and the earth wire dangling in mid space ,ie not
bonded, the bonding pipe clamp was perfectly secure.
So was it flexing of the sink , every time of using the taps, caused the
leak and undoing of that screw or something like waterhammer, not ever
heard any water hammer though.