Needhelp regarding Water connection cut by society

Q: There is water logging issue happening in a flat below my flat . Other flat owner is always suspecting this is due to some problem in my bathroom . Both the parties are staying here since more than 5 years .
There might be internal leakage problem, however please note that neither it has developed over period of years nor is due to any modifications done by me in my bathroom. Other flat owner has been getting this problem checked from Day 1, & hence in my view this is a STRUCTURAL defect.
My bathroom is in same condition without a single modification/alteration done since I have taken handover the flat from the builder. Only thing done was white cement filling in bathroom tiles to avoid any water leakage & that was also done to avoid any possible leakage.
A very important point here is the other flat owner is a committee member & has strong hold in society .
I have already initiated communication with builder to get the problem checked & repaired to resolve the issue .
In recent development Society has cut the water supply to my bathroom & on enquiring society supervisor told me , this will be connected back only when you get your internal repair done & problem is resolved.
I need expert advice here what options I have to tackle this scenario. Please help with any contact pointers if you can provide me.