Hi,
We came down to our dining room (in the middle floor of our 3 floor townhouse) to discover there was a collection of water on our dining room table that seemed to have come from the ceiling above it(middle floor ceiling). Since we had bought the house about 15 months ago, we called up the previous owners to see if they had ever encountered a similar problem in the past. The previous owner informed me that sometime in the mid-90's(approx 10 yrs ago) or so, he had had a leak in the same area and it turned out to be that was some sort of a crack in the Washer Drain pipe that was leading to the water leak in the ceiling below. He said he had hired a plumber to replace/fix the pipe and the replace the drywall/ceiling and it had cost him around approx $300-400.
Although the strange thing is that we don't notice the leak when we run the washer, but instead when we run the shower there seems to be a pool of water than somehow makes its way on the floor between the tolilet and the tub. We are almost positive that this water is not coming from the shower directly, since we've made sure that we keep the shower curtain secure.

Any ideas what's going on? The previous owner claims that he never had any problems with the bathrooms?

" The previous owner claims that he never had any problems with the bathrooms?"
Well it sure sounds like you have a problem in there now. What kind of a shower do you have? Custom tile? Fiberglass or plastic enclosure? You're going to hafta localize and pin point the source of the leak. Let's start with the shower pan, drain, trap and drain line. Remove the strainer and block off the dtain by blowing up a balloon in the drain or packing a wet sock in it. Tonight before bedtime fill the pan with a inch or so of water and let it set overnight. Cover the downstairs table with plastic. In the morning check for moisture or wet spots. Now let the water go out the drain and check again.
If there's no moisture the chances are that the water's coming in where the stream hits the tile wall. Over the years tile grout shrinks and allows water to run down the wall behind the lip of the pan. The solution is to waterproof the tile grout. Good luck and let me know what you find. Regards, Tom