Legality of usage of Metro Water from Common Sump by one of owner

Hi Sir, We live in an apartment consisting of 15 flats in Chennai, Tamil Nadu. One of the owner had put a separate water connection to the common metro water sump. This was disputed amongst other residents saying the owner is taking undue advantage, as he is not letting the water flow to the overhead tank before getting distributed to all houses. This was addressed to the owner in the monthly meeting and after a great commotion, pipes and motor were removed. The association bore the expense of relaying new pipe line to his house from the overhead tank. Now the owner is contesting to relay the pipes & motor again to the sump directly, thereby fetching water from the sump directly instead of letting it flow to overhead tank for distribution. He claims to have a legal opinion that this is valid? Is this true? How can one person take metro water directly from the common sump before going to common overhead tank? Please advise?