What mantra is recited during Pind Daan?

The core Pinda offering mantra is: Om Adya [Gotra]-gotraya [Name]-sarmanah esa pindate svadha. The most powerful mantra is the Jal/Dugdh Dhara mantra from the Rigveda: Om Urjam vahanti amrtam ghrtam payah kilalam parisrutam, Svadha stha tarpayata me pitrin – recited 3 times while pouring the milk-water stream. Always use Svadha (not Svaha) at every step of the ritual.