Please clarify the issue of rinsing dishes before placing in a dishwasher.

In the previous shiur we learned that certain requirements must be met to permit loading a dishwasher on Shabbos, on account of hachana – preparing for after Shabbos.

One may only rinse dishes before loading them into the dishwasher if done in order to prevent residue sticking. If performed to enable the dishwasher to operate properly, it is prohibited.

Why the distinction?

I once heard a definition of hachana as follows. An action that cannot be done after Shabbos may be performed on Shabbos and is not hachana; an action that can be done after Shabbos may not be performed on Shabbos on account of hachana.

Rinsing dishes on Shabbos to prevent residue sticking cannot be done after Shabbos, because by then the residue will have stuck fast. Rinsing dishes to enable a dishwasher to operate properly can be done after Shabbos as well and as such that action is hachana.

A common way to define non-hachana is to say that prevention is not hachana. For example, returning food to the fridge on Shabbos is not hachana, although one does not intend on consuming that food till after Shabbos, because it is preventing the food from spoiling. Our abovementioned definition explains this heter as well.

May a gentile wash my dishes in hot water?

A general rule regarding amirah le’akum (instructing gentiles) is that if a permitted manner exists the gentile may do it in any manner seen fit by the gentile.

The source for this rule is the Taz, [1] who says that a light a gentile switches on to wash dishes is not a light switched on for a Jew, because the Jew does not derive the direct benefit from it. Rather the dishes are rinsed in the light.

Similarly we can compare rinsing dishes in hot water by a gentile to switching on the light. The Jew does not derive direct benefit from the hot water and the gentile is doing it to complete the task that he/she is obligated to perform.

What if the dishes cannot be cleaned without hot water?

In that case Rav Shlomo Zalman Auerbach ztz”l writes, [2] that the gentile may not heat water for that purpose, because the Jew derives benefit on Shabbos from extra clean dishes. If the hot water is used on account of cold weather or to rinse the dishes quickly, [3] it may be so done, because the task can be performed in a permitted manner. See the footnote with regards to a gentile using the hot water system. [4]

May a gentile wash my dishes in a dishwasher?

Since the gentile is able to perform the task in a permitted manner, i.e. rinse dishes manually, he may wash them in a dishwasher. [5] However, this involves yet another issue.

In the Rama it states (according to one opinion) [6] that a Jew may not operate appliances that emit noise before Shabbos that continue to operate on Shabbos and can be heard outside the Jew’s home, lest people think that he commenced operating them on Shabbos. It is known as a zilzul of Shabbos – dishonor to Shabbos. On the other hand, appliances that are known to operate before Shabbos, such as clocks, may be set before Shabbos to operate on Shabbos because everyone knows that they are set before Shabbos.

Dishwashers, washing and drying machines might be subject to this constraint.

Some opinions prohibit the use of a dishwasher, even when operated by a gentile, on account of this halacha, [7] while others permit it. [8] It generally depends on whether it is a newer model and cannot be heard outside the kitchen. A rav should be asked.

What must be avoided when washing dishes?

Several issues:

• A sponge. One may not use a sponge, even one that sports a handle, on account of ‘squeezing’. [9] One may only use a utensil that does not contain water. Steel wool is also prohibited even though water is not absorbed within the fibers. It can be compared to squeezing hair, which is ossur mid’rabanan – rabbinically prohibited even though water is not absorbed in the hair.
• Hot water. The hot water tap should not be used for two reasons. The first is because cold water usually enters the heating system. (This has been discussed at length in previous shiurim). The second is because sometimes hot water melts fat clinging to dishes and involves nolad – changing form. [10]
• Soap. Solid soap must not be used. [11] Several poskim prohibit use of liquid soap unless it is very watery. This can be accomplished by adding water before Shabbos to regular soap. Other poskim permit using liquid soap as long as it can be poured. [12]