As the resident electrician I was called by a plumber to isolate the electrics at an army cook house the other day due to a flood.
Now imagine a 3 storey building with a plant room on the top floor. The plumber had the task of pumping out a cold water storage tank on the top floor which he had just chlorinated to kill any bugs. He had put a sump pump in the tank and passed the hose through a grill so the water would run onto a sloping roof below, then into the gutter.
Unfortunately what he didnt realise is that the hose as it was fed out found its way through an open window on the floor below. So the water was pumped into an unoccupied office on the first floor and then seeped through the floor to the main kitchen area on the ground floor!