Kashering a Dishwasher

A dishwasher washes at high temperature, so it absorbs, and it requires kashering rather than cleaning alone.

The procedure

1. Clean it thoroughly of all food residue — the base of the cabinet, and every hole and crack in it. Clean the trays, racks and baskets too.
2. Wait twenty-four hours.
3. Boil water in it, and when it is boiling, run the machine with the trays, racks and baskets inside. The boiling water kashers the machine and its fittings together.

The racks going in with it is the part people miss. They are as much in contact with the dishes as the cabinet is, and kashering the machine without them leaves the job half done.

When racks cannot be kashered

Two cases where a rack is replaced rather than kashered:

• Holes or cracks holding dirt that cannot be cleaned out. Where the residue cannot be removed, do libun kal at those points.
• Materials that cannot take libun — plastic and similar. These must be replaced with new ones.

Since most modern dishwasher racks are plastic-coated wire, this is a live question rather than an edge case. Coating that has chipped, exposing wire that then corrodes and traps residue, is exactly the situation described.

The filter and the seals

Reading the first step carefully: "every hole and crack" in a dishwasher means the filter housing, the sump, the spray arm jets, and the door seal. These hold food in a way the visible cabinet does not, and a machine cleaned only where you can see it has not been cleaned to the standard the procedure assumes.

Running meat and dairy

Using one dishwasher for both is a substantial question in its own right — not merely a cleaning matter — and practice varies considerably. That one belongs with your rav rather than with a general procedure, and it is worth settling before you organise your kitchen around an assumption.

See also the three methods of kashering.