From a kashrut point of view, a modern dishwasher is by far the most complicated appliance in the kitchen. What goes on inside is the following:
If the dishwasher heats water to yad soledet bo, then the dishwasher is acting like an oven and is "cooking" the dishes inside. Ashkenazic Jews therefore restrict use of the dishwasher to either meat or dairy dishes.
So what if you make a mistake and put a meat dish in your dairy dishwasher or vice versa?
This exact case is brought in the Shulchan Aruch, though in a large vat of boiling water used for washing dishes rather than in a dishwasher. For both Ashkenazic and Sephardic Jews, b'dieved we say that all the dishes involved remain kosher. We say this for several reasons:
Thus if you find that you accidentally washed your dairy dish with your meat dishes in the meat dishwasher, everything is permitted b'dieved. For similar reasons, if you find a meat dish in your cabinet among the dairy dishes or vice versa, everything remains kosher.
Similarly, if you accidentally washed your pareve dish with your meat dishes in the meat dishwasher, they remain pareve. Whether or not you can do this l'chatchila is debatable; discuss it with your rabbi.
Questions to ponder:
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