Well I'm facing the same leakage problems as we speak now and the different is only that mine is condo and yours landed now.

As for condo I'd to pay for affected unit and communicate with them and management, very super leceh.

For landed if it's washroom u can opt to not use the current host and redo a new 1 without hacking....a lot landed doing this....
2nd option is you hack but dunno which part if causing the issues and would take times to identify and costly....

Both requiring water proofing, 1 way is using self DIY e proxy if the toilet is seldom use and less wet kind else for long run need redo the water proofing depending on your size ranging at a minimum of 2k onwards...good luck