24 Mar PARSHAS TZAV: KASHERING A DISHWASHER FOR PESACH

An earthen vessel in
which it was boiled
shall be broken; if it
was boiled in a copper
vessel, [the vessel]
shall be scoured and
rinsed with water.

Vayikra 6:21
Introduction
Dishwashers are among the modern-day
appliances that have helped ease much of the
strain of maintaining a clean home. Although
dishwashers cannot be used on Shabbos or
Yom Tov, they nevertheless improve people’s
oneg Shabbos and simchas Yom Tov by
allowing them to enjoy the day and postpone
washing their dishes and utensils until after
Havdalah. They would certainly be an asset on
Pesach if they can be kashered from their
normal chametz status. The main questions
that must be clarified are whether it is possible
to kasher a dishwasher at all and, if it is, if that
applies to Pesach as well.
Methods of Kashering
There are two main methods of kashering,
both of which are based on pesukim (Vayikra
6:21; Bamidbar 31:23) – hagalah and libun.

Hagalah refers to immersing the item into
rapidly boiling water, thereby allowing any
flavor (ta’am) that was absorbed (balua) into
the walls of the kli to escape into the water.
Libun is a method of eradicating the flavor by
burning it directly with fire or extreme heat to
the point that it becomes charred. The method
of kashering that is used is determined by the
manner in which the ta’am became balua in
the kli. If the kli absorbed the ta’am through a
liquid medium (e.g., a pot boiling on a
stovetop), one can kasher it using hagalah. If
the flavor was absorbed through direct heat
(e.g., a grill grate or roasting pan), it must be
kashered using libun.
Since hagalah only releases the ta’am into the
boiling water but does not eradicate it, the
poskim suggest that in order to perform
hagalah most effectively, the kli should not be
used for twenty-four hours prior to the process.
In this way, the ta’am absorbed in the kli will
be deemed stale (nosein ta’am lefegam), such
that even if it is reabsorbed into the pot after
being drawn out of the walls by the boiling
water, it is not considered problematic
according to Halacha.
Issues Specifically Related to Dishwashers
The original discussions regarding kashering

dishwashers are largely not relevant today, as
they centered around the possibility of
kashering porcelain. Dishwashers
manufactured in the last few decades do not
contain porcelain; they are generally
comprised of metal and plastic. The central
question is therefore whether it is possible to
kasher plastic. The other significant problem
with kashering a dishwasher relates to whether
it is possible to properly clean it of all of the
hidden food particles that gather over the
course of the year.
Kashering Plastic
It is scientifically accepted that plastic is a
porous substance capable of absorbing ta’am.
The question relevant to kashering plastic is
thus whether the ta’am can be released in the
manner in which it was absorbed. Should we
compare plastic to metal, which absorbs and
releases ta’am in the same manner, or should
we compare it to earthenware, which absorbs
ta’am but does not fully release it?
The Tzitz Eliezer (4:6) and Rav Ovadiah
Yosef (Chazon Ovadiah 2) rule that it is
possible to kasher plastic. In contrast, Rav
Moshe Feinstein (Igros Moshe, OC 2:92)
maintains that although plastic can be
kashered during the year, it cannot be kashered
for Pesach.
How to Kasher a Dishwasher
If one is kashering a dishwasher during the
rest of the year, or if one accepts the view of
the poskim who hold that one can kasher
plastic, what would be the appropriate
manner in which to kasher a dishwasher?
Generally, a dishwasher absorbs the ta’am
of the food when hot water is splashed on
both the food and the surfaces of the
dishwasher. It should therefore be kashered
using hagalah. The main problem with doing
hagalah on a dishwasher is that it is not
possible to maintain a steady boil inside the
dishwasher in order to apply it to all of the
surfaces that have come into contact with
food.
To solve this problem, some poskim
recommend placing an even milubenes, a
red-hot stone or brick, inside the dishwasher
while it is running, which will help boil the
water. Although this method may be helpful,
however, it is not fully effective, as it only
helps boil the water that is in direct contact
with the brick.
It is therefore necessary to rely on a sevarah
offered by many poskim, including Rav
Soloveitchik and the Aruch HaShulchan. If a
kli absorbs ta’am only at a particular
temperature, it can be kashered at that same
temperature, even if it is below the normal
heat level required for hagalah or libun.
Accordingly, if, for example, the water
inside a dishwasher reaches only 180
degrees, it is not necessary to kasher it at the
normal boiling point of 212 degrees, as 180

degrees is sufficient. This reasoning is based
on the Gemara’s understanding of the principle
of kebolo kach polto, that flavor is expelled in
the same manner in which it was absorbed.
While we generally require the water to be
brought to a boil, since the utensil that we are
kashering might have been used with boiling
water, these poskim allow for kashering at
lower temperatures for utensils that can never

reach a hotter temperature due to pre-
determined settings in the appliance.

The Main Problem with Kashering a
Dishwasher
Rav Moshe points out that the problem with
kashering a dishwasher is that it contains parts
that cannot be properly cleaned of food
particles. Although hagalah works to remove
any bliyos absorbed in the walls of a kli, it
does not help if there are non-kosher or
chametz food particles that are contained
within the kli. Rav Moshe refers specifically
to food getting stuck on the racks, which does
not seem to be an issue in today’s dishwashers,
but other parts, such as small vents and filters,
are indeed very difficult to clean. Thus, one
who relies on the poskim who permit
kashering plastic and allow for hagalah with
sub-boiling temperatures must be careful to
clean the dishwasher thoroughly prior to
running a cleaning cycle to kasher it.
Conclusion
It is clear that the question of the permissibility
of kashering a dishwasher is subject to a
difference of opinion among the poskim.
Some forbid kashering plastic altogether,
others permit it but not for Pesach, and still
others permit it if one fills the dishwasher with
hot stones or bricks. It is also possible that one
can kasher a dishwasher for Pesach by merely
raising the temperature of the water prior to
running a cycle. In order to account for the
possibility that there is variation in water
temperature, some rabbis suggest running the
dishwasher several times, with the expectation
that at least on one cycle it will have reached
its all-time high temperature.
Rav Hershel Schachter has ruled that plastic
may be kashered for year round use but may
be kashered for Pesach only in cases of great
need; this would apply to dishwashers with
plastic or rubber racks. Rav Schachter permits
kashering metal dishwashers even for Pesach
and even in cases without great need.