Kaun Kitne Paani Mein is a story about two fictitious villages Upri which is made up of upper caste but extremely lazy and people lacking any productive skills and Bairi made up of lower caste people who have been involved in labor work and hence have gained a lot of skills. The people of Upri and Bairi are loggerheads with each other as generations back there was a murder suicide due to cast issues by the then Maharaja ruling the then rich and upper class Upri village.
As time went Upri has seen water shortage due to their lack of skills and Bairi has instead become prosperous. Maharaj Braj Singhdeo (Saurabh Shukla) the leader of Upri, survives on his reputation and is almost bankrupt now and doesn’t even have money to send his son Raj Singhdeo (Kunal Kapoor) to college. On the other side Kharu Pahelwan(Gulshan Grover) is a prosperous MLA candidate from Bairi village whose daughter Paro(Radhika Apte) supports him intellectually and morally. Raj convinces his father Braj to plan and get resources from Bairi village by molesting or marrying Paro and to execute this plan Braj pretends to throw Raj out of his household. Raj goes on to live with Kharu as his assistant and slowly gets into the good books of Amrita Devi(Hema Singh) the president of the ruling party who Kharu represents. But Raj also falls in love with Paro.
Braj Singhdeo plans an elaborate fraud with the assistance of Amrita Devi, Raj, a tailor who has dug a canal underground to suck water from Bairi and the temple priest to make believe goddess has intervened to get the villages to be united and that Raj and Paro should be married. The villages end up living peacefully together and Raj gets political mileage and becomes an important leader in Amrita’s party.