Wastage of water

How can I file a complaint against water wastage ? Where can I file a complaint ? I stay in Virar east at Kargil Nagar, the building behind our building are the chawl type building 4 floors, everyday the water from the tank on the top of their building keeps on flowing and no one is bothered to come up and close it, unless we shout from our gallery. Here in some part people are not getting water they need to call for the tankers even that is possible once in 2 days. These people are getting the water but have no value to it. I really want them to be aware or if possible let them feel the pinch how it feels when they will be without water.