The Questions (and Answers) of BDJ

Access a printable PDF version of this essay here.

Iyyar 26, 5784 

June 3, 2024 

Although it has been the normative practice among Ashkenazic Jews to designate their dishwasher as either “dairy” or “meat” (henceforth “milchig” or “fleishig”), i.e. to not wash milchig and fleishig loads in the same machine, there is strong halachik reasoning to adopt a more lenient approach in light of technological advancements in the effectiveness of dishwashers. Rav Yosef Tzvi Rimon, a leading halachik authority in Isarel laid out the argument for using our dishwashers for milchig and fleishig consecutively, and concluded that we should feel free to do so, as long as certain details are attended to. I found Rav Rimon’s arguments and conclusions to be persuasive (not that he needs my approval!), and I wanted to share it with our community, hoping to make our lives easier. This essay explains and presents the conclusions of Rav Rimon’s p'sak halacha (halachik ruling).  . (You can read a Hebrew summary of his position here.) 

PART ONE: The Early Masters 

The original prominent Halachik authorities who wrote about dishwashers were Rav Ovadia Yosef z”l and Rav Moshe Feinstein z”l. Rav Ovadia took a particularly permissive approach, permitting even the simultaneous washing of milchig and fleishig dishes in a dishwasher. His p’sak, which was broadly adopted in the Sephardic world, was based upon a halachik position taken by the Shulchan Aruch (Yoreh De’ah 95:4). There, the Shulchan Aruch permits the washing of “dishes that have meat fat stuck to them” inside a milchig pot filled with hot water, as long as ashes (which I believe functioned as soap for them) had been added to the water. His reasoning is that the ashes render the food residue “pagum”, i.e. unpalatable to the point of halachik irrelevance, obviating any possible violations of the meat-and-milk laws. Rav Ovadia extends this argument to the soap that we mix into the water in the dishwasher which, he ruled, allows even for the washing of milchig and fleishig dishes together in a dishwasher.  

Two important notes to Rav Ovadia’s p’sak: (1) Several of the (Ashkenazi) commentators on the Shulchan Aruch questioned whether in fact ashes render food “pagum”, as they observed correctly that this assumption lacks precedent in earlier halachik literature. Much of Ashkenazic p’sak halacha has therefore tended to not invoke the Shulchan’s Aruch’s position (except in cases in which other factors for leniency were also present).  (2) Some contemporary Sephardic scholars have questioned the relevance of the position in light of the way that most modern dishwashers now function. In most modern dishwashers, the soap is placed in a compartment which only opens at some point after hot water has already been swishing around the cavity of the dishwasher for some time on its own, potentially mixing residue from a previous load with the food remnants in the present load.  

Rav Moshe Feinstein also took a permissive approach, though he approached the issue completely differently, and he didn’t go so far as permitting the milchig and fleishig dishes to be washed simultaneously, rather only in consecutive loads. Rav Moshe did not invoke the “ashes / soap” argument at all. He rather invoked the principle known as נ”ט בר נ"ט דהתירא. (“a double—transfer of permissible “ta’am”).  Here’s how this principle works: 

1. Generally speaking, the reason we use pots and dishes for milchig food or fleishig food but not both is that even after the food residue has been washed off, “ta’am” (the invisible-yet-halachikly-significant absorption into the walls of the pot or dish  remains. This “ta’am” can re-emerge the next time this pot or dish is used with hot food, and just as we are forbidden to mix actual meat and milk, we are also forbidden to mix the “ta’am” of meat and milk.   
2. But the נ”ט בר נ"ט דהתירא principle limits the number of times that “ta’am” can transfer and still remain halachikly relevant.  “Ta’am” of a permissible (i.e. kosher) food is relevant  in its first and second transfers but not beyond. So in our case: “ta’am” of meat (for example) which had entered the walls of the dishwasher in load #1, is released into the hot water when the next (milchig) load is initiated. But as soon as it enters the hot water it is neutralized and can no longer cause any halachik trouble for the milchig dishes.  

Rav Moshe also considers an additional halachik concern, that of actual food residue that may still be in the machine after load #1. He dismisses the significance of actual residue that may be on the walls of the machine, on the grounds that this residue will invariably be nullified 60:1 in the water of load #2.  He is however more concerned about actual residue that might be remaining on the dishwasher’s racks. His concern is that if a milchig dish is placed on a rack that happens to have physical fleishig residue on it from a previous load, then this fleishig residue will get onto the milchig dish. And then the hot water will hit this fleishig+milchig amalgam and instantly render the dish not kosher. This is what led Rav Moshe to add the caveat that while the dishwasher itself can be used for consecutive loads of milchig and fleshing, the racks cannot. His recommendation that people own two separate sets of dishwasher racks historically proved to be too onerous / expensive, resulting in the normative Ashkenazic practice to simply designate the dishwasher as either milchig or fleishig.  

PART TWO: Nowadays 

Rav Rimon argues that all of this deserves a new look in light of changing habits and changing technology. The common habit that we have is to rinse dishes before we place them into the dishwasher, leaving only the very small amount of food that is literally stuck to the dish.  This practice even further increases the likelihood of 60:1 nullification in the water, and reduces the likelihood of food remnants remaining anywhere in the dishwasher by the end of the load. But the primary change that Rav Rimon highlights is the technological one, which has given us dishwashers that are so effective that we are able to actually see with our own eyes that there is in fact NO discernable residue to be found anywhere after a load, including on the racks. Rav Rimon suggests that Rav Moshe would have no objection to our using these dishwashers for consecutive loads, even with the same racks. He in fact points to a responsum that Rav Moshe wrote a year after his original one, in which he permits consecutive milchig and fleishig use of an industrial dishwasher presuming that the dishes were rinsed before being placed therein, and in which he makes no mention of the caveat about racks whatsoever.  

Although this is already sufficient halachik basis to use our dishwashers for both milchig and fleishig loads (not milchig and fleishig in the same load), Rav Rimon doesn’t rest here, but insists that we additionally utilize Rav Ovadia’s basis for leniency – the presence of soap. He addresses the above-mentioned questions concerning Rav Ovadia’s p’sak by: 

(1) distinguishing between the ashes that the Shulchan Aruch had discussed, and dishwasher soap that we use today. Soap is so much more pungent and unpalatable than ashes, that even if one were to question the halachik effect of ashes on residual food particles, one cannot doubt the effect of soap. (It should also be pointed out that there were also several Ashkenazi masters, such as Aruch HaShulchan, who had endorsed the Shulchan Aruch’s “ashes” position to begin with.) 

(2) instructing us that in addition to placing the dishwasher detergent in the compartment that will only open after hot water is already circulating in the dishwasher, that we also place some soap in the main cavity of the dishwasher, thus ensuring that soap is present from the first moment that water first enters the machine.  

Rav Rimon adds that as an additional precaution we should – a few times as we are starting to use the dishwasher for both milchig and fleishig loads - check the filter (or “trap”) at the bottom of the dishwasher before using it, to confirm that the machine isn't leaving significant pieces of food therein.  If it is, then the filter should be routinely cleaned out between loads. 

In conclusion, it is permissible to use our dishwashers for milchig and fleishig loads consecutively as long as we adhere to the following guidelines: 

1. We do not wash milchig and fleishig dishes simultaneously in the same load. 
2. We habitually rinse the easily removable food particles off our dishes before we place them into the dishwasher. 
3. We place some soap in the main cavity, in addition to the soap that we place in the designated soap compartment. 
4. We confirm that our machine isn’t leaving significant pieces of food in the filter / trap.  

Finally, please note that this does not extend to using a chametz dishwasher for Pesach. Dishwashers still require koshering for Pesach.  

Thanks for reading, and please share questions!