Switching on a dishwashers on Shabbat involves the issur melacha of both ‘havarah’ -creating a fire, and ‘bishul’ – cooking the water.
The first question which raises interesting issues is the use of a time switch which is set before Shabbat that will operate it on Shabbat. what are the halachic issues involved in this? Firstly there is a remarkable ruling of HaGaon Rav Moishe Feinstein ztza’l which is a blanket prohibition of all uses of timeswitches to operate machinery on Shabbat, except lighting and heating. The reasoning behind this is complex, but for those who totally follow his rulings this question of dishwashers or any appliances on automated systems on Shabbat is forbidden. However, many rabbonim do not follow this chumra ruling.
The real halachic issue here requires some understanding of the the way in which the dishwasher functions. In particular it is the effect of opening and closing the door of the dishwasher which creates an halachic problem. The door is designed with a micro-switch in the handle that will ensure the machine only works when the door is shut. This is a safety feature in case someone opens the door mid-cycle that it will instantly shut off the machine and it will only restart when the door is shut. If one sets the dishwasher on a timeswitch and then on Shabbat loads the dishes into the machine while it is off, there is as yet no halachic problem. However, the closing of the door is an action which indirectlycauses the re-starting of the machine when the timeswitch activates it later on. If the door is left open it will never switch on, even when the timeswitch goes on. We therefore view the act of closing the door as an indirect cause of the operating of this machine and the boiling of the water. This in halacha is called ‘gramma’.
A technical solution to this has been applied in some communities in Israel to supply a dishwasher with a ‘shabbat switch’ which de-activates the switch in the handle. One could also get an electrician to disable the switch permenantly. This solves the halachic problem, but is firstly not an easily available solution, nor is it recommended for everyone as it creates a health hazard if one opens the door mid cycle it will continue spraying very hot water.
The general topic of indirect causes – ‘gramma’- is a widely applied principle in the halachic system affecting all sorts of topics from property damages to machine baked matzos, but here in the context of Shabbat the Mishna states that there is no violation of a melacha mideorrayta when the action performed is one of ‘gramma’. The example of the Mishna (Bavli Shabbat 120a) is stopping the spread of a fire on Shabbat where there is no possible danger to anyone, only a monetary loss, and direct extinguishing of fire is forbidden, one may put jugs filled with water at a distance from the flame such that when it spreads to the jugs they will burst and put out the fire. This is the main source which permits ‘gramma’ indirect causation on Shabbat. Following this principle it would appear to be permitted to close the door of the dishwasher and thereby indirectly activate the machine at a later moment when turned on by the timeswitch.
However, the Rema (Shulchan Aruch O.H. 334.22) rules that since this source is dealing with stopping the spread of flames, we only know that ‘gramma’ is permitted in order to prevent monetary loss, and he therefore limmits the leniency to cases of preventing monetary loss, or other forms of extreme circumstances, such as treating illness or to enable performance of a mitzva. The final ruling that emerges therefore is that simply for purposes of convenience or to minimise effort we do not allow ‘gramma’ and the use of a dishwasher on a timer on Shabbat would be forbidden.
A second practical question is regarding the use of a dishwasher on shabbat by a non-Jewish employee in a Jewish home. In general (with some exceptions of illness, extreme cold etc.) it is forbidden mi-derabbanan to ask a non-Jew to do any sort of work on shabbat for a Jewish person which the Jewish person himself is not permitted to do. (Shulchan Aruch. O.H. 276) However the non-Jew is of course allowed to do any sort of work he wishes to do for his own benefit. An interesting issue arises in cases, not uncommon, where the a non-Jewish employee is required to do a particular job, in this case wash the dishes after a meal, and in order to make it easier to complete the job he wants to switch on the dishwasher. The Jewish householder is clearly forbidden to instruct that the dishwasher be used, but do we regard this as a case where the ‘work’ of switching it on is being done for the benefit of the non-Jewish employee in which case it is allowed, or is it being done for the benefit of the Jewish householder in which case it will be forbidden. That’s the question. A similar case would be the employee required on shabbat to sweep the floor and decides to make it easier by using a vacuum cleaner. This is a classic borderline halachic case where we will need an authoritative precendent from within the halachic literature in order to make a ruling.
The relevant precendent is found in a ruling of the Taz, (Rabbi David Halevy in 17th cent Poland, in his commentary at the end of the O.H. 276) where the non Jewish employee in the Jewish home has the duty to clean the dishes after the meal, but it is Friday night and the kitchen is totally dark. In order to do her work she must light the candles in the kitchen. Is one allowed to ask her to was the dishes in this circumstance? this is a good precedent for our question, do we regard her as lighting the candles for herself in order to do her work in which case it is permitted, or do we regard her as lighting them for the Jewish householder in which case it is forbidden. In fact the Taz rules that this is permitted to ask her to do the dishes even knowing that she will light the candles for herself in order to do so. This would appear to give us a clear result, permitting the use of a dishwasher or the vacuum cleaner a by non-Jewish emloyee in a Jewish home, in order to make her work easier.
However there is a futher issue to consider in the halacha. Chazal were concerned that we should not have on Shabbat loud noises of machinery which will disturb the peaceful Shabbat atmosphere. This is referred to as ‘avsha millsa’ – an aramaic term. (Shulchan Aruch O.H.252.5) The example given is the water-driven mill of the ancient world which could be filled with wheat before shabbat and left by itself to grind it into flour during the Shabbat. This was forbidden on account of the noise it generated which would detract from the ambience of a restful Shabbat. Exactly how much noise is required in order for this to be a problem is not clear, but it seems to be the case that it has to be a noise of such level that at least will be heard throughout the house.
Interestingly on this basis there may be a difference nowadays between the case of the dishwasher as opposed to the vacuum cleaner. Certainly in my house and those I have visited, one cannot hear the noise of the dishwasher unless one stands in the kitchen, but the vacuum cleaner can be heard in the whole house. The ruling I have given therefore is as follows: the non-Jewish employee who is obliged to wash the dishes is allowed to use a dishwasher on shabbat to make the work easier for him/her self. But may not be instructed to do so by the Jewish householder. However the use of the vacuum cleaner could only be done with a very quiet model which I have yet to see!