Pitru Tarpan in the month of Pitrapaksha is a must ritual to perform for your ancestors. Tarpan over the river Ganga makes your ancestors happy & they provides moksha to the departed soul.
Your ancestors in the heaven always wishes happiness for you & in return if a pilgrim offers Tarpan & Pind daan to them they feel happy & bless you on behalf. The ritual of Tarpan & Pind daan has great importance in Ramayana & Mahabharata. Among hindus, it is must to perform in the month of Pitra-paksh.