Make sure to perform milui ve-irui (filling and pouring) before the end of the fourth hour of the day before Passover.  This is the same as the time that is announced, as the latest time one may eat hammets. After this time and throughout Passover itself, only libbun gamur or libbun kal may be used to kosher utensils.

Step-by-Step Guide

1.   Make sure that the vessel to be koshered was not used for twenty-four hours.

2.   Fill the vessel to the top with water (the water need not be hot).

3.   Leave it so forat least 24 hours.

4.   Pour out the water.

5.   Refill and leave it for at least another 24 hours.

6.   Pour out the water.

7.   Refill and leave it for at least another 24 hours.

8.   Pour out the water.

What Are the Uses of Milui Ve-irui?

This process is mentioned in Shulchan Aruch (our code of law) as an effective method of koshering in the following cases:

1.   Prohibited wine is left in an earthenware vessel (even if it is left there for a short time).

2.   Prohibited wine is placed in a vessel in which wine normally remains for a long timeeven if, in this instance, the wine does not remain for a long time. This applies to metal, wood and so forth, but not to glass. For more details, click here.

3.   A type of liquor that is hammets—such as whiskey—is left in a vessel for more than 24 hours. Milui ve-irui is an effective way of koshering the vessel for Passover.

From the above two cases—the case of prohibited wine and the case of hammets liquor—it appears that milui ve-irui would be effective any time a prohibited liquid became absorbed in a vessel.

This is not the case.

The poskim (halachic authorities) limit the use of milui ve-irui to cases similar to the two above cases. They explain that the sages were lenient in the case of prohibited wine. And they were lenient in the case of hammets because of a concept called hetera bala’ (at the time the hammets was absorbed—before Passover—it was permitted).

For a comprehensive A-Z listing of how to kosher various utensils and appliances for Passover, click here