822. Rinsing the Utensils

116:16 One may only kasher through immersion utensils that have not been used for more than a day, i.e., more than 24 hours has passed since chometz was cooked in it. The pot in which the utensils are immeresed must also be unused for more than a day. One must check that each time he puts a utensil in the pot, the water is still boiling. If one needs to kasher the pot itself, then when the water is boiling and the pot is full, he throws in stones heated to glowing so that the boiling water overflows the top of the pot. Kashering by immersion should only be done until midday on erev Pesach.

116:17 After kashering by immersion in boiling water, the practice is to rinse the utensils in cold water. (The intention is that one should do so immediately after hagalah but the kashering is still effective even if one doesn't do so at all - Mishnah Brurah 452:34.)