Unequal sharing of Common resourses such as water in an apartment complex.

I am a resident of an apartment complex in Chennai consisting of 8 houses. The water plumbing of the complex to individual houses has technical issues that favor certain houses (the ground floor residents) and goes against the interests of certain residents of the floors above the ground floor. Chennai is facing acute water shortage at this time of the season. As a result, whatever amount of water that is pumped onto the overhead tank for common consumption is being solely utilized by the ground floor residents and few of the upper floor residents. Houses at the very top (including mine) don't receive even a drop of water due to this situation. Water being a common resource of the apartment isn't being shared equally. Technically the problem can be easily solved by changing the plumbing of the flat in a manner such that all the houses get equal share of water. This setup isn’t being accepted by the ground floor residents who turn belligerent when suggested. (They fear their water supply will be diminished as it would now be equally shared by all the houses). I am at a loss of knowledge in as to who to approach and complain in a manner that would help solve this situation.