I hope all is well.
What is the status of water if it was poured from a kli rishon into a traif cup (its treif because it was used as a kli rishon)? Where exactly can I find the source for those type of halachos.
Assuming that the cup was cold, the water that was poured will only pull out, “kdei lipa” – a peels worth of tate from the treif cup. Therefore determining factor of the water depend if there is shishim to nullify the treif taste of the cup. Additionally, if the cup was not used in the last 24 hours, and the taste that came out of it would be rendered sour, (nosain ta’am lifgam) and b’dieved it would not make the water treif. The halachos are scattered throughout issur v’heter. Look in Y:D 98-1, 95-3, 91-4.