Tarpaṇam — Satisfying Through a Prescribed Water Offering
Tarpaṇam (from the Sanskrit root tṛp, 'to satisfy') is the ritual offering of water with prescribed mantras for the satisfaction of the addressed devas, ṛṣis or pitṛs. The recipient, occasion, hand position, direction, sacred thread position, ingredients and mantras differ according to the rite.
Distinct Forms
Vedic practice contains several forms of tarpaṇa. Deva- and ṛṣi-tarpaṇa may occur in the contexts appointed by one's sūtra, including Brahma-yajña. Pitṛ-tarpaṇa is performed on occasions such as Amāvāsyā and in connection with śrāddha according to eligibility and family practice. Sesame and darbha are important in specified pitṛ rites, but they are not universal ingredients of every form of tarpaṇa. Likewise, the pitṛ-tarpaṇa of Amāvāsyā is a distinct observance and is not simply identical with every daily Sandhyāvandanam; any tarpaṇa elements within Sandhyā practice follow the practitioner's own Vedic recension.
The Three Debts
Tarpaṇa belongs within the wider Vedic acknowledgement of obligations to devas, ṛṣis and ancestors. It is an act of gratitude and dharma, not an attempt to treat the departed as independent divinities. For a Śrī Vaiṣṇava, Nārāyaṇa is understood as the antaryāmin and ultimate receiver who empowers the devas, ṛṣis and pitṛs addressed in the appointed rite.
Sampradāya Discipline
The exact procedure is learned from one's family elders, Vedic teacher and Āchārya in accordance with śāstra. Differences of sūtra and regional practice are therefore preserved rather than replaced by one universal sequence.