First, consider mutual relations in a small society between permanent neighbors. Involve some other flat owners and let them explain the law that in anticipation of some other future seepage, the other party is not having a right to claim for advance repairs with his fears or assumptions. Meanwhile, contact other societies or your neighbours and learn about the practice. Finally, if he succeeds in a court, then act as per Court decision. The cause of action arises only when there is leakage or seepage or likely such dangers in future viewed as per past experiences. When there is no cause of action, there is no lis.