RTI can be used to get information from government authorities. We cannot instruct the government to take any action.
We can ask information which will help us find how their actions have been. You can file RTI to the Municipal Corporation asking for the information and reasons for non supply of water.
Also, you can file a complaint regarding the same to the concerned authority. If you don't get a reply, you can file RTI to know the status of the complaint and the action taken on it. Make sure you keep a copy of the same.