So some of it will already be happening:
A leaky hose on the washing machine, a heavy downpour of rain with the window open and it's done:
A water damage.

Well, if you will be warned in time to keep the damage to a minimum.
For this purpose lends itself to a water detector that effort with little can be done by the laity themselves crafted.

Here you may find Circuit, Basics, Schematic Diagram and DIY Kit components for Water Detectors