If you own a property with a seemingly endless supply of water, you should have one of these installed:http://www.watercop.com/
This is small electric motor with a radio receiver, mounted on a 1" dia valve that gets installed near the pressure regulator/water shutoff by the water heater...
You have these wireless transmitters about the size of a deck of cards connected to a sensor. Powered by a pair of AAA batteries.
When water is detected, they beep (helps you figure out which one tripped or is about to have dead batteries) and about a second later, the water supply is shut off for the entire house.
It would have saved my only flood disaster if I hadn't tried replacing the faucets myself in a bathroom I never use, so I didn't put one of the wireless leak detector/radio transmitters in that bathroom.
That was so much fun, seeing water cascading through the floor down to the garage below.