a friend was sharing a water leak problem

- 5 storey walk up apartment
- bought the 4th floor unit

apartment has several 'stalactite' mineral deposit from the roof. several inches from ceiling coming down.

- found that the problem comes from the toilet upstairs.
- owner upstairs refuse to repair their toilet

my friend did PU injection however water flow now to a wall. the wall looks like coloured. if look carefully, probably got fungus / mold.

any suggestion how to fix the problem without upstairs help ?

tks so much