How to kosher a dishwasher

Many families use the dishwasher for meat and dairy dishes in separate cycles. Here is what it takes to kosher it.

The dishwasher poses a particular challenge because its internal walls, filters and spray arms are in constant contact with food residue at high temperature, which can absorb flavors more persistently than other appliances.

The dishwasher is one of the most debated appliances: its filters and spray arms hold residue at high temperature. Photo: Myke2020 via Wikimedia Commons, Public domain.

Why it generates so much rabbinic debate

Unlike an oven or a set of pots, a dishwasher has dozens of hidden crevices, a filter that traps food particles directly, and spray arms that recirculate hot water loaded with residue throughout the entire cycle. That combination makes some authorities treat it more strictly than almost any other appliance, and a few discourage using the same unit for both meat and dairy altogether, even on different days.

The procedure for those who do allow it

Thorough cleaning of filters, spray arms and rubber seals, removing every visible particle by hand.
Not using the dishwasher for 24 hours before koshering it.
Running a full empty cycle at the highest possible temperature, ideally with a strong cleaning product.
In some communities, it is recommended to use separate, interchangeable racks or trays for meat and dairy, rather than koshering the entire appliance between uses.

The alternative that avoids the problem at the root

Many families sidestep the debate entirely by using removable rack baskets or dedicated racks, one for meat and one for dairy, that go in and out of the same machine. Since the food itself never touches the machine's walls or filter directly, some rabbinic opinions consider this a much simpler solution than repeated koshering.

Differences between communities

Customs vary quite a bit on this topic — some Sephardic and Ashkenazi communities differ notably in how strict they are about dishwashers specifically. This is one of those cases where it is well worth consulting directly with the congregation's rabbi before deciding how to organize the kitchen, rather than assuming the same rule that applies to hagalah for pots also applies here.

Frequently asked questions

Is a dishwasher with a sanitizing high-heat cycle automatically easier to kosher?
It can help reach the required temperature faster, but the debate is less about temperature and more about the machine's internal structure and how food residue circulates inside it.

Do plastic dishwasher racks need separate koshering?
Plastic parts are generally treated differently from the metal interior; ask your rabbi about the specific model if this comes up.

Does using rack baskets fully resolve the issue for every community?
Not universally — some more stringent opinions still prefer a fully dedicated machine per category. It is worth confirming the criterion your community follows.