I use a metal teapot to make “tea essence” with teabags and boiling water before Shabbos.
If I washed the teapot in a milchig dishwasher on Sunday, can I use it next Shabbos to make tea and drink it with a fleishig meal?
Yes you may. The reason for this is because the teapot is not a “ben yomo”, and coupled with the fact that the water is a “nat bar nat” (reabsorbed taste), according to many poskim it is permitted l’chatchila. Here it is even better because you are only using for tea which you are not actually drinking with the meat, rather afterwards.
Understandably for the future this is not something that should be done l’chatchila.
Rama Y”D 95-2, Gra ibid -10, Madanei Osher 66-2, Ben ish chai 2 kKorach 13. Even according to the Chochmas Odom 48-2, who says that we not cook in it l’chatchila in order to eat it with the opposite type, we have another factor here, that it isn’t being eaten actually together with the meat, rather afterwards for dessert, see Rema 89-3, and “The laws of Kashrus” pg 241 2b.
Besides there are other factors here, it isn’t clear that the teapot Is indeed milchig, depending on how the dishwasher washes, if the detergent is distributed together with the first water or only afterwards, if there was actual milchigs in the dishwasher at the time, and even so was it more than shishim of the water in the dishwasher, to make the teapot milchig.