I'm wondering if our plumbing gurus have any tips on where to locate the source of leaks in pipes that are in walls, floors or ceilings without having to take out huge portions of the surface areas in order to locate the leaks.

Case in point: I have an elderly friend with an upstairs apartment in one of the homes that she owns. When it got really cold, she neglected to shut off and drain the pipes to an adjoining bathroom and kitchen upstairs. The home is unoccupied, so leaving the heat up was something that she didn't want to do.

The result was, that one or more pipes burst or had leaks develop in them. Walls and floors in a downstairs foyer had water coming down a couple of the walls as well as through the ceiling above the foyer.

Are there any tips or tricks to finding where the leaks are without tearing out huge portions of the walls and ceiling downstairs and maybe upstairs floors and walls too? I know that the water can travel, and finding out such a thing might not be possible without tearing apart vast areas.

I've learned a lot from the plumbing pros on this site!