Water from floor above
Water is a little sneaky. A very small leak can do a great deal of damage. That is what these homeowners experienced. The source of this damage was a leaking hose under a bathroom sink in the upstairs bathroom. The leak was small enough that nobody really thought much about it, but it was obvious it was leaking for a long time before it made itself apparent.
The ceiling in the master bedroom below started to drip because the drywall had become completely saturated with water. The homeowners were noticing a "musty smell" for some time, but couldn't identify the source until the water began dripping from the ceiling.
They called SERVPRO of Southeast Milwaukee County and we were able to identify and correct the problem. We removed the damaged drywall, and due to this water having an organic odor we removed the affected carpet as well.
Moral to the story....when you see even the smallest amount of water, find out where it is coming from and get that problem corrected quickly.