Leakage from above floor

Dear Group

I am the owner of the flat in Ahmedabad and the there is leakage from above floor flat (mostly because of broken pipe)  that is creating a spot on my bathroom passage which is increasing gradually. Above floor flat is occupied by a tenant and he is generally out from morning till night for work purpose. The owner of the flat lives in Assam and his relative is taking care about the flat. I have informed the relative  (person taking care about the flat) regarding the leakage. He is not refusing but is delaying the repair matter saying that flat is always closed as tenant comes late at night, how can he manage repairs and bla bla..

Under this circumstances, I want a legal opinion taking into account following matters

1) Our flats are not co-operative society. Sale is made directly by the stamp paper and there is no share certificate. But we have a association. In this case has society any role to play??

2) Above flat is generally closed. So how can i send a legal notice with registered post?? What is the option if the flat is closed and there is no one to receive the notice??

3) Which civil law section can be applied, if a legal path is sought? Or consumer law is applicable in this matter??

4) Most important, approximately what time frame can it take to end the case??

An early reply is highly thanked with.

Thanking you.