The sink drain

Hi,

One may rinse a plate in the sink on Shabbat without concern for filtering in the drain of the sink; the food remains in the drain, and the liquid is not being separated from any solid.

(Rav Moshe Feinstein, Igrot Moshe Orach Chaim 4:74 Boreir 4)

המצפה לישועה,
Mordechai