Tuesday, May 28, 2024

The Great Dishwasher Debate

Although we live in a world of technological advancements and achievements, and their impact on halachah can seem complicated and confusing, Klal Yisroel has been blessed through the ages with poskim who have enlightened us as to the practical application of halachah in these areas. Rav Shlomo Zalman Auerbach zt”l, in particular, among other gedolim and poskim, was known to relish hearing about technological advances and demonstrating how the halachah still applied to it, for as we know, “ain kol chodosh tachas hashemesh, there is nothing new under the sun” (Koheles 1:9). In this spirit, this article will focus on the intricacies and the issues the poskim deal with in deciding the halachic status of a not-so-recent technological advancement: the dishwasher.

Theoretical questions:

1. Do I really need separate dishwashers for my meat and milk dishes?

2. By accident, my dishwasher washed my milchige and fleishige dishes together. Do I need to throw everything out?


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

This is 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 botel beshishim and halachically considered nullified).1 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) fleishige pot to cook macaroni and subsequently place the macaroni on a plate and then mix them with cheese, is that considered bosor becholov?

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 apply, 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 bliyah (absorbed taste) of meat into the pot.

2. The bliyah from the pot into the macaroni.

3. The bliyah from the macaroni into the cheese.

So, it is not considered bosor becholov, since there are (at least) two degrees of separation in between them. Note that this hetter, however, only applies by bosor becholov. It does not apply by bliyos of issur or treif.2

There is much discussion in the poskim as to the parameters of this din. The Shulchan Aruch (Yoreh Deah 95:1) rules that Nat Bar Nat is a hetter even lechatchilah, while the Rama (ad loc. 2) argues that one may only rely on this bedieved. That means, according to the Shulchan Aruch, that (back to our example) if one would use a clean, ben yomo fleishige pot to cook macaroni and subsequently place the macaroni on a plate, he would be allowed to mix cheese into the macaroni.3 According to the Rama, 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.

“Okay. 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 (ad loc. 3), following the lead of several Rishonim, including the Rosh, Ramban and Rashba (in their commentaries to Chullin, Perek Kol Habosor 112a), 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 or mamashos (literally substance), there would not be a transfer of taste, for this, too, would be considered a Nat Bar Nat occurrence and therefore permitted.

The Rama, however, following the precedent of other Rishonim, including the Sefer Haterumah, Ran, Mordechai and Tosafos (ad loc.), 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 rules that this case would not fall under the category of the hetter of Nat Bar Nat, and the dishes would be considered non-kosher.4

Nevertheless, the Rama does allow room for leniency if these clean dishes were washed in the same water one after another. 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 the dishes would be permitted. The basic halachah follows the Rama on this.

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

Dishwashing Din

Rav Moshe Feinstein zt”l, in numerous teshuvos,5 rules that one may use the same dishwasher for both milchige and fleishige 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 the one dairy dishes and one for the exclusive use of the meat dishes.6

He maintains that since the hetter of Nat Bar Nat applies regarding 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, there will always be shishim (60 times the amount) of water against any actual food residue, so one does not have to worry about the food leftovers actually making the dishwasher assur. 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. Next week’s article will further discuss in detail the various other opinions and issues related to the halachic aspects of the dishwasher.

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1. Barring specific circumstances, this is the standard rule of nullification in halachah. If there is 60 times the amount of non-kosher present, it is considered nullified. See Shulchan Aruch Yoreh De’ah 98.

2. Important note: There are numerous scenarios and similar sounding cases in which the din may be very different (for example, many poskim are machmir that there is no hetter of Nat Bar Nat regarding roasting). Therefore, one may not pasken for oneself based on this article. The halachah 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 shailah in this and all other halachic matters.

3. 3 Although there is some debate, this description follows the basic understanding of the Shulchan Aruch’s opinion lemaaseh, as per the majority of authorities, including the Issur V’hetter (34:1), Shach (Yoreh Deah 95:3), Taz (Yoreh Deah 94, Daf Acharon, s.v. assur), Pri Chodosh (Yoreh Deah 95:1) Be’er Heitiv (ad loc. 5), Kreisi Upleisi (ad loc. 1), Bais Lechem Yehudah (ad loc. 3), Knesses Hagedolah (ad loc. Hagahos on Bais Yosef, end 20), Pri Megadim (ad loc. Mishbetzos Zohov 4, end s.v. ul’inyan), Kehillas Yehudah (ad loc.), Zivchei Tzedek (ad loc. 2), and Kaf Hachaim (ad loc. 1). This follows the precedent of several Rishonim, including the Smak (213), Hagahos Maimoniyos (Hilchos Maachalos Assuros 9:23), Rabbeinu Yeruchum (Sefer Adam, Nesiv 15, vol. 5:28; pg. 137, fourth column), and the Mordechai (Chullin, 708 and 754). Accordingly, even though the Shulchan Aruch would hold that Nat Bar Nat is lechatchillah, he was referring to once the cooking was already done; now it comes into play and one may now rely on it lechatchillah. However, one may still not cause a Nat Bar Nat. A good example would be cooking noodles in a fleishige ben yomo pot in order to later mix it with cheese; this would still be prohibited. However, if it was already cooked in such a pot, the Shulchan Aruch would hold that one may now mix in cheese. On the other hand, there are several contemporary Sefardic poskim, most notably Rav Ovadiah Yosef zt”l (Shu”t Yabia Omer, vol. 8, Yoreh Deah 43:1-5) and Rav Shlomo Amar (Shu”t Shama Shlomo, vol. 1, Yoreh Deah 2, and vol. 2, Yoreh Deah 5), who maintain that the main intention of the Shulchan Aruch (as per his Bedek Habayis amendments to his Bais Yosef commentary, beg. Yoreh Deah 95, s.v. kasav rabbeinu) is to allow one to even be “gorem Nat Bar Nat lechatchillah.” Others who rule this way include the Tefillah L’Moshe (vol. 3:12) and the Yalkut Yosef (Issur V’Hetter, vol. 3, pgs. 30-31 and 420-425). Conversely, other poskim, including Rav Shalom Meshash (Shu”t Mizrach Shemesh 98; Shu”t Shemesh Umagein, Yoreh Deah 8, and his responsa published in Shu”t Shama Shlomo, vol. 2, Yoreh Deah 4 and 6) and Rav Mordechai Eliyahu (cited in sefer Ikkarei Hashulchan on Bosor Becholov, pg. 225; see also Shu”t Vayaan Yitzchok, Yoreh Deah 4, who rules similarly), argue that the halachah follows the majority opinion of the Acharonim in their understanding of the Shulchan Aruch’s shittah. Although for Ashkenazim this machlokes yields no practical difference, on the other hand, as the Shulchan Aruch’s true intent is debated by contemporary Sefardic poskim, a Sefardi must ascertain from his own knowledgeable posek which opinion to follow lemaaseh.

4. 4 See Tosafos (Chullin 111b-112a, end s.v. hilchasah). This understanding is followed by many other Rishonim, including the Smak, Smag, Shaarei Dura, Hagahos Maimonios, and Issur Vehetter. This shittah is also the haskomas haposkim. See the nosei keilim to Yoreh Deah 95:3, including the Shach, Taz, Biur HaGr”a, Be’er Heitiv, Chavas Daas, Pri Megadim, Chochmas Adam and Aruch Hashulchan.

5. 5 Shu”t Igros Moshe (Orach Chaim, vol. 1:104, s.v. uvadovor; Yoreh Deah, vol. 2:28-29; Yoreh Deah, vol. 3:10, 2 and 11 and 58, s.v. vechein).6. The need for a second set of racks according to Rav Moshe’s shittah is due to the fact that the dirty dishes sit directly on the racks. It stands to reason that these racks will consequently more readily absorb direct ta’am from the food residue. Therefore, if one would place dirty milchige and fleishige 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 bosor becholov.
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Rabbi Spitz serves as the sho’el umeishiv and rosh chaburah of the Ohr Lagolah Halacha Kollel at Yeshivas Ohr Somayach in Yerushalayim. For the full mareh mekomos (sources) or to share comments or questions, email the author at yspitz@ohr.edu.



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