How Do I Dispose of Crumbs and Leftover Chametz on Shabbat?
Written by Rabbis Eli Gersten, Yaakov Luban, and Moshe Zywica of the Orthodox Union
Leftover crumbs from the dishes, table or floor should be swept and flushed down the toilet before the end of the fifth (halachic) hour. If the floor needs to be swept, one should make sure the broom is free of crumbs. Larger pieces of chametz may be broken into smaller pieces and flushed down the toilet.
Alternatively, large pieces of chametz may be placed in outdoor garbage pails, provided there is an eruv, but the chametz must be rendered inedible by pouring bleach or ammonia over the entire surface of the chametz. One must be certain that the bleach or ammonia saturates the entire piece of chametz. These fluids must be designated for that use before Shabbat, otherwise they would be muktzah.