Kashering Dishwashers for Pesach - Part II by Rabbi Chaim Jachter


Last week we discussed the issue of kashering a dishwasher lined with porcelain.  This week we will discuss kashering a dishwasher with a metal or plastic lining.

Dishwashers - Can They be Kashered?

In his responsum to Rabbi David Stavsky concerning a dishwasher for Pesach, Rav Moshe Feinstein (Igrot Moshe Orach Chaim III:58) writes that a metal-lined dishwasher may be kashered provided that it can be cleaned thoroughly (a thorough cleaning is critical to any proper kashering).  Indeed, there are classic examples where Chazal believed that certain utensils could not be kashered because they were difficult to thoroughly clean (see Rabbeinu Tam's explanation of Pesachim 30b cited in Tosafot Chullin 111a s.v. , Shulchan Aruch O.C. 451:3 Rema O.C. 451:18 and Mishna Berura 451:56).  Indeed, the Mishna Berura 451:156 writes that "any utensil that one cannot extend his hand into [in order to thoroughly clean it] cannot be Kashered."

For this reason, many Poskim (unlike Rav Moshe) believe that one should not kasher a dishwasher for Pesach due to concerns that it cannot be cleaned thoroughly.  A dishwasher's many nooks and crannies are the focus of this concern.  Similarly, many rabbis have a similar concern regarding microwave ovens (Rav Moshe Feinstein apparently didn't share this concern as he permitted kashering a microwave for Pesach).  They point to the many holes and crevices which it is reasonable to say cannot be cleaned thoroughly for Pesach Kashering.

How To Kasher a Dishwasher

If one believes that metal dishwasher may be kashered, the question is how to kasher it.  The basic rule for kashering is articulated in Bamidbar 31:23 - that which became not kosher through contact with fire must be kashered with fire, and that which became not kosher in a water medium, must be kashered in a water medium (in last year's Kol Torah for Pesach we examined this issue at length in our discussion of kashering ovens for Pesach).  Rashi explains that the inherent principle is    - the way the utensil was used (for non-kosher usage) is the way it becomes kosher.  The Talmud (Pesachim 30b) articulates  the rule thus:   , the way the utensil absorbs non-kosher taste particles is the manner that the taste particles are expelled.  Rav Moshe writes to Rabbi Stavsky that when kashering a dishwasher, a hot brick must be placed inside the dishwasher to boost the temperature of the water to boiling.  This is based on the practice that when kashering with water, the water must be boiling (see Taz Yoreh Deah 94:3 and Mishna Berura 452:8).  In other words, even though the dishwasher water temperature never reaches higher than 190NF when in use, the practice is that kashering always requires boiling water.

However, Rav Mordechai Willig and Rav Yosef Adler quote Rav Soloveitchik as disagreeing.  The Rav believes that only when one is not certain at what temperature the water was when the utensil became non- kosher, is boiling required.  However, when one is absolutely certain that the temperature of the water when in use with non-kosher (or Chametz) products never went beyond a certain level, then   , the object may be kashered at the highest temperature the object was ever used with non-kosher food.  Thus, since one is certain of the maximum temperature of the dishwasher, he may kasher the dishwasher [after leaving it unused for at least 24 hours] simply by running the dishwasher through a full cycle, since he is certain that he is thereby kashering the dishwasher with water reaching the highest temperature the water in the machine the water ever reached when in use with non- kosher utensils.  The Shaar Hatziyun (451:196) seems to support the Rav's contention that one may kasher at the highest temperature the water reached in use with non-kosher dishes, because of the rule of   . 

Plastic Lined Dishwashers- Rav Moshe's Opinion

Many dishwashers today are lined with plastic.  The question is, how do contemporary authorities categorize materials not discussed in the Talmud?  In Igrot Moshe O.C. II. 92, Rav Moshe writes to Rav Ephraim Greenblatt of Memphis that one may not kasher synthetic rubber "since it is new and not addressed in the classic sources, one may not kasher it."  The same would apply for plastic items according to Rav Moshe's approach.  Rav Moshe's approach to this question is quite surprising, especially in view of the fact that the Igrot Moshe is replete with application of Halacha to an incredibly wide variety of issues?  It seems that Rav Moshe's responsum was issued solely in regard to Pesach, as Rav Shimon Eider (Halachot of Pesach p. 138 note 10) writes that Rav Moshe permits plastic to be kashered for year-round use other than for Pesach.  Apparently, this is another of many examples of "Chumra D'Chametz," a special Pesach stringency.  Parenthetically, it seems somewhat puzzling that Rav Feinstein permitted a microwave to be kashered for Pesach, as its inside is coated with plastic.  (Rav Mordechai Willig told this author that for this reason he believes that one should not kasher a microwave for Pesach.)

Kashering Plastic - Other Opinions

Rav Moshe's opinions regarding avoiding kashering synthetic materials seems to be a minority voice among contemporary authorities.  Indeed, Rabbi Eider (Halachos of Pesach p.138 note 10) quotes Rav Yosef Eliyahu Henkin who rules that plastic does not even need to be kashered because it is smooth and does not absorb (  ).  Although Rav Henkin's view is a minority view, many contemporary authorities permit kashering plastic even for Pesach.  Rav Eliezer Waldenburg (Tzitz Eliezer 4:6) permits kashering plastic utensils for Pesach, as does Rav Gedalia Felder (Yesodei Yeshurun VI: 170-173) in case of need.  For these authorities, as long as a utensil does not contain earthenware it may be kashered.  Only regarding earthenware does the Torah tell us that it can never have all of its absorbed taste particles expelled by kashering.  Indeed, Rav Yechiel Yaakov Weinberg (Teshuvot Seridei Eish 2:160) writes that the accepted practice is to kasher plastic.  Rav Weinberg does not limit his permissive ruling to non-Pesach use.  Other authorities who permit plastic to be kashered include Rav Yaakov Breisch (Teshuvot Chelkat Yaakov) and Dayan Weisz (Teshuvot Minchat Yitzchak 3:67).  The Maharsham (3:233) also permits a utensil made of synthetic material to be kashered.  Indeed, the Pri Megadim (Mishbetzot Zahav 451 s.v.  ) writes explicitly that "earthenware is the only material that may not be kashered."


We have seen arguments on both sides of the issues as to whether metal or plastic dishwashers may be kashered for Pesach. Accordingly, one should consult with his Halachic advisor regarding this issue.  May we all merit kashering our ways and become an even finer people!



            A former member of the Brookline, Mass. community told this author that Rav Soloveitchik consistently permitted members of his Shul to kasher porcelain coated dishwashers for Pesach, even without changing the racks.

            It should be added that when Rav Feinstein permitted kashering a porcelain dishwasher in case of significant monetary loss, he required that the racks be replaced.

Kashering a Microwave Oven for Pesach by Rabbi Chaim Jachter

Kashering Dishwashers for Pesach - Part I by Rabbi Chaim Jachter