Gated community apartment - certain issue

No I am residing in a big enclave in Madurai (Tamil Nadu). I am in ground floor and corner flat . My flat No. LG-3 ( L=Block, G=Ground Floor, 3=Flat #). There is leakage of drainage water from the bath room of the flat, which is over my flat . That flat No.LF-3 (L=Block, F=First Floor, 3=Flat #). The leakage of the drainage water from the bath rooms of LF-3 causing heavy damages of my bath room’s wall and roofing. The steel which has been used for belt of the wall and roofing concrete itself have been heavily damaged/stained and the stained steel brown colour is visibly noticed in my bath room wall. You know pretty well that this kind of damages will certainly spoil the stability of the building. Since this is a gated community with five floors apartment, I can not do any thing at my own accord in this regard. I have given a complaint petition to the General Secretary of our association stating these facts and to take necessary steps. But no any action from association side. The flat owner (LF-3) is denying to carry out the repairs in his bath room. Because he is not residing in that flat. He let his flat for rent and one tenant is occupying in LF-3 flat. Now I want to file a suit in the court. If so, to whom I have to send lawyer notice, ie., Flat Owner or The General Secretary of the association? I shall be ever grateful to you, if you could help me in this regard. Thank you, RAMARAJ.S Mobile. 9442967161