Insights into Halacha

For the week ending 14 July 2012 / 23 Tammuz 5772

The Dishwasher Debate - Part 1

by Rabbi Yehuda Spitz
The Color of HeavenArtscroll

Although we live in a world of technological advancements and achievements, and their impact on halacha can seem complicated and confusing,thankfullyKlal Yisrael has been blessed through the ages with authorities who have enlightened us as to the practical application of halacha in these areas. Rav Shlomo Zalman Auerbach zt"l, in particular, among othercontemporary decisors, was known to relish hearing about technological advances and demonstrating how the halacha still applied to them. In this spirit, this article will focus on the intricacies, as well as the issues, the poskim deal with in deciding the halachic status of a not-so-recent technological advancement: the dishwasher.

Common Questions:

  1. Do I really need separate dishwashers for my meat and milk dishes?
  2. By accident, my dishwasher washed my milchig and fleishig dishes together! Do I need to throw everything out?

Assuming your dishwasher is not your significant other, in which case one should suffice to wash all your dishes (of course not together), this is a somewhat complicated question, and, in order to properly answer it, we must first gain at least a basic understanding of the complex halachic issues involved.

Nat Bar Nat (or Not Bar Not): Degrees of Separation

Not (no pun intended) the name of someone mentioned in the Gemara, nor the latest Jewish music song (yet!), this is actually the term used to define indirect taste transfer. Nat Bar Nat stands for “Nosein Ta’am Bar Nosein Ta’am”. A Nosein Ta’am refers to a direct transfer of taste. For example, if one would cook a nice, hefty cholent with meat inside, the meat would transfer direct taste into the rest of the cholent, rendering the entire cholent fleishig (unless of course the chef was a little too stingy in the meat department and the miniscule piece was battel b’shishim, andhalachically considered nullified). A Nosein Ta’am Bar Nosein Ta’am refers to indirect, or secondary, transfer.

Case in point:

If one would use a clean, ben yomo (used within the last twenty-four hours) meat pot to cook macaroni, and subsequently placed the macaroni on a plate and then mixed it with cheese – is that considered bassar b’chalav, the Biblically forbidden mixing of meat and milk?

The answer is no, it is 100% permissible to eat, for there was no direct contact between the meat and the cheese, only a weak secondary contact. This is known as Nat Bar Nat. In order for this hetter to occur, the meat and milk must be at least twice removed from each other: (Think of the branches on a family tree – Uncle Earl might be directly related to you, but that does not really make him related to Cousin Edna.)

There is the transfer of:

  1. The bleeyah (absorbed taste) of meat into the pot.
  2. The bleeyah from the pot into the macaroni.
  3. The bleeyah from the macaroni into the cheese.

So it is not considered bassar b’chalav, since there are (at least) two degrees of separation in-between them. Please note that thisleniency only applies to bassar b’chalav; it does not apply by bleeyos of issur or treif[1].

There is much halachic discussion as to the parameters of this rule. The Shulchan Aruch[2] holds of Nat Bar Nat even l’chatchila, while the Rema maintains that one may only rely on this b’dieved[3]. That means, according to the Shulchan Aruch, (back to our example) if one would use a clean, ben yomo meaty pot to cook macaroni, and subsequently placed the macaroni on a plate, then he would be allowed to mix in cheese with the macaroni[4]. According to the Rema, however, only if one already mixed in the cheese would it be permissible to eat; if he had not yet done so, it would be forbidden to mix them together in order to eat the macaroni with cheese.

“O.K. While it is always nice to be enlightened about a halachic concept," one might say, “what does this have to do with dishwashers?”

The answer is “everything”.

Washing Dishes = Nat Bar Nat?

The Shulchan Aruch, a few paragraphs later[5], equates our case of noodles to washing dishes. He states that even if one washed milk and meat dishes together, as long as the dishes themselves were clean of actual pieces of residue, there would not be a transfer of taste, for this too would be considered a Nat Bar Nat occurrence, and therefore permitted.

The Rema, however, argues that since the dishes would be sitting together in the same boiling water at the same time while washing, there will be a direct transfer of ta’am.He therefore paskens that this case would not fall under the category of the hetter of Nat Bar Nat, and the dishes would be considered treif.

Nevertheless, the Rema does allow room for leniency if these clean dishes were washed in the same water one after each other. He maintains that since there is no actual mixing of absorbed taste of meat and milk simultaneously, it would be considered Nat Bar Nat, and consequently the dishes would be permitted. The basic halacha follows the Rema on this.

That said, even though the Shulchan Aruch was referring to washing clean dishes in boiling water, this halacha still translates to dishwashers.

Dishwashing Din:

The great Rav Moshe Feinstein zt”l, in many responsae,[6] rules that one may use the same dishwasher for both meat and milk dishes, provided that it is not used for both types of dishes at the same time and that it is cleaned out (along with an empty rinse cycle) in- between uses. He also requires one to maintain separate racks, one for exclusive use of dairy dishes and one for the exclusive use of the meat dishes[7]. He maintains that since the hetter of Nat Bar Nat applies to dishes being washed consecutively even in the same water, accordingly, the hetter certainly applies to dishwashers, where the second set of dishes is washed in separate clean water. Additionally, a full dishwasher will always contain 60 times the volume of any actual food residue, so one does not have to worry about the food leftovers actually making the dishwasher assur[8]. Therefore, as long as one sticks to these important details, Rav Moshe maintains that one may use the same dishwasher for both meat and milk dishes separately.

However, it is important to note that many contemporary authorities express reservations about Rav Moshe’s psak for various reasons. IY”H next week’s article will further discuss in detail the various other opinions and issues related to the halachic aspects of the dishwasher.



[1]Important note: There are numerous scenarios and similar sounding cases where the din may be very different (for example, many poskim are machmir that there is no hetter of Nat Bar Nat by roasting); therefore one may not pasken for oneself based on this article. The halacha presented here is simplified to present the issues in an understandable manner. One must ask a competent halachic authority for guidance in case of an actual sheilah in this and all otherhalachic matters.

[2]Y”D 95, 1.

[3]Y”D 95, 2.

[4]This is according to the basic understanding of the Shulchan Aruch’s intent. (Shach Y”D 95, 3).

[5]Y”D 95, 3.

[6]Shu”t Igros Moshe (O.C. vol. 1, 104 s.v. uvadavar; Y”D vol. 2, 28 & 29; Y”D vol. 3, 10, 2; ibid 11; ibid. 58 s.v. vchein).

[7]The need for a second set of racks, according to Rav Moshe’s opinion, is that since the dirty dishes sit directly on them, they will more readily absorb direct ta’am from the food residue. Therefore, if one would place dirty milchig and fleishig dishes on the same rack, (even in two separate cycles), this may result in the racks absorbing both meat and dairy taste. This then transmits together to the dishes in a subsequent load as ta’am basar b’chalav.

[8]This is the standard rule of nullification in halacha.If there is present 60 times the amount of non-kosher, then it is considered nullified. See Shulchan Aruch Yorah De’ah 98.


Disclaimer: This is not a comprehensive guide, rather a brief summary to raise awareness of the issues. In any real case one should ask a competent Halachic authority.


L'iluy Nishmas the Rosh HaYeshiva - Rav Chonoh Menachem Mendel ben R' Yechezkel Shraga, Rav Yaakov Yeshaya ben R' Boruch Yehuda, and l'zchus for Shira Yaffa bas Rochel Miriam and her children for a yeshua teikef u'miyad!

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