Water from the ceiling, but it's not raining... oh no

Nope, it's not rain; it's bad plumbing. I'd really like to kill the previous owners, not to mention the home inspector  and the plumber I hired right after I moved in to fix another fuck-up.

When someone tells you "We've replaced all the plumbing," wouldn't you assume that statement to mean all pipes in the house running to the city sewer line have been replaced? Apparently that would be a false assumption. The old cast iron main pipe that all the drains connect to was not replaced. They simply punched holes in it and let the new pvc pipe dangle in it. I had to pay for that little understatement 2 years ago right after I bought the house and the toilet started backing up. I had the plumber check the upstairs bathroom as well; he said everything was hunky-fucking-dory up there. Wrong again.

They ran new pvc from the toilet and the sink, lopped off the old iron pipe in the attic where it plunges into the floor/ceiling, then dangled the pvc over the ragged opening of the iron pipe. I guess it's been working fine all this time, but my son clogged the toilet up, and when he freed the clog it must have sent a rush of water that overflowed the opening and ran into the ceiling. How lucky am I?

Hopefully I'll have enough room up there that I can get one of those rubber boots on to splice the two pipes together. If not... well, I'd rather not think about that right now. I guess I'll find out this weekend. Wish me luck - I have a feeling I'll need it.