3 tanks by each floor on Terrace

Hi i have recently purchased top floor along with roof rights of a 4 floor residential building in delhi (typical builder floor with stilt parking, lift etc). The other 3 floors (G, I and II) were already occupied by respective owners. To my surprise I see that 2 of the previous residents have installed 3 tanks each in the terrace: 1) 1 500 litre tanker initially installed by builder (for MXD water supply) 2) 1 extra 1000 litre tank (which they used for underground Boring water earlier but later discontinued boring water and connected this 1000litte tank also with MCD water motor) 3) 1 shared 1000litre tank for backup. They use water from this spare tank when there is water supply shortage and their main tank gets empty All these things extra tanks are eating into my space and when i requested the Other residents to rationalise this they insist that this was existing before me. What are my rights here? Also, is there a limit by Govt on how much maximum storage capacity (in litre) or number of tanks is allowed?