Narayan Nagbali / Tripindi Shraddha vidhi should performed to get rid of Pitru Dosh. Performing these poojas' during the period (5th to 19th September) of Pitrupaksha(पितृ पक्ष) will be more beneficial. According to the Hindu calendar Pitrupaksha starts immediately after the Ganesh festival and ends with the New moon day know as Sarvapitri amavasya. The Hindus offer homeage to their ancestors during pitrupaksha to get their blessings and help their soul attain the path of Heaven.
According to Hinduism, the souls of three preceding generations of one's ancestor reside in Pitru–loka, a realm between heaven and earth. This realm is governed by Yama, the god of death, who takes the soul of a dying man from earth to Pitru–loka. Hindus are expected to propitiate the ancestors(let the ancestors be in peace) in the first half, during the dark fortnight i.e Pitru Paksha and let the soul of their ancestors reach the Heaven from the Pitru-loka.
When a person of the next generation dies, the first generation shifts to heaven and unites with God, so Shraddha offerings are not given. Thus, only the three generations in Pitru–loka are given Shraddha rites, in which Yama plays a significant role. According to the sacred Hindu epics, at the beginning of Pitru Paksha, the sun enters the zodiac sign of Libra (Tula). Coinciding with this moment, it is believed that the spirits leave Pitru–loka and reside in their descendants' homes for a month until the sun enters the next zodiac—Scorpio (Vrichchhika)—and there is a full moon. Hindus are expected to propitiate the ancestors in the first half, during the dark fortnight.