Stoppage of water supply from overhead tank

The building where I am staying consists of 14 flats. I am staying in 2nd floor approved flat and water supply to my flat has been stopped stating that 2nd and 3rd floor unapproved flats are not getting water when overhead tank is filled and let out. Instead they illegally used a hose directly from the motor and let out water in the first floor. What legal action can I take against these people who are causing me trouble and nuisance by stopping water supply to my apartment. All the pipelines from the overhead tanks are concealed.