Upper floor owner not fixing water leakage

Hi I'm from Bangalore , I'm the Flat owner residing on 3rd floor , There is a constant leakage in my balcony from the flat situated at the 4th floor , I personally brought the notice to 4th Floor owner ( who is also a builder of this apartment ) , he commented saying the leak is from terrace & asked to check with person who is in charge of Maintenance , I spoke to Maintenance guy he has done some water proofing in terrace & asked to wait for 2-Weeks , now 2 weeks is over still the water leakage is happening , also now leakage started inside my master bedroom , so I'm worrying now as my family is compel to residing in unhygienic condition , I brought this notice to Maintenance guy , he told verbally that issue is b/w owners & ask to check with 4th floor owner , I again informed to 4th floor owner , but till now no action taken . Can I legally issue a lawyer notice , Also this problem started after recently 4th floor owner done his bathroom renovation , that why we strongly suspect leakage is from his bathroom , also can court ask to stay usage of that bathroom Or water supply cut to that bathroom until the issue resolved ( as 4th floor owner denying it is not from his toilet ) , its been more than 3 weeks now , so I kindly request to suggest me the way .