Water Filters and Purifiers
Question: Is it permitted to use a water filter or purifier system on Shabbos to enhance the taste of the drinking water?
Discussion: It is forbidden on Shabbos to use a sieve or a sifter or any other utensil designed for selecting to remove impurities or debris (pesoles) from drinking water (ochel). It makes no difference if the bad is being removed from the good or vice versa; it makes no difference if the selection is being made for immediate use or not; either way it is violation of borer min ha-Torah since an implement which is designed for selection is being used68. But this is only forbidden if the water is so dirty that it will not be drunk in its present state by most people. If the water is presently drinkable, yet it is being purified or filtered for extra cleanliness, it is permitted to remove the impurities even with a sieve or a sifter69. Similarly, using an installed filter or purifier system to clean water which is drinkable as is but is being filtered or purified for extra cleanliness, is permitted per all views70.
Question: Due to a possible infestation concern of copepods in the water system in certain parts of New York, some people have installed a faucet-based filtering system which does not allow the copepods to enter their drinking water. Is it permitted to use a filter system on Shabbos for the purpose of filtering out infestation71?
Discussion: It follows, based on the previous answer, that it should be forbidden to use a filtering system which is designed to block the copepods from the water. Since the infested water may not be drunk in its present state, it is halachically classified as a mixture of good (ochel) and bad (pesoles), and selecting one from another using a utensil designed to do so is forbidden. Indeed, some poskim rule that one who is strict not to drink copepods-infested water, may not use a filter to clean the water on Shabbos72.
But this ruling is widely debated by many poskim, and indeed, some poskim permit using an installed filter or purifier system on Shabbos even when the purpose is to avoid the copepods. There are several arguments that can be made in support of their view73:
When using a teapot, Chazon Ish74 rules that it is permitted to pour essence through the strainer in the spout even if the essence is mixed with the leaves, provided that it is being poured for immediate use. While there are several different ways of explaining this difficult-to-understand ruling,75 there is a strong similarity between a faucet with a filter and a teapot with a strainer, and if the teapot is permitted as per the Chazon Ish, the filter system is permitted as well.
Some Rishonim76 maintain that the prohibition of borer, which means to remove bad (pesoles) from good (ochel), applies only to the removal of physical pesoles, e.g., impurities which render the ochel unfit to eat or drink, such as dirt, bugs or repulsive material. Copepods, which are hardly visible to the naked eye,77 are not considered “impurities” to the water companies, their customers or to the regulating agencies. In halachic terms, they are not considered pesoles at all; borer, therefore does not apply.
These and other arguments are part of the debate on whether or not filter systems are permitted on Shabbos. As mentioned, there is no consensus among contemporary poskim in this area. As always, for final halachic ruling consult your posek.
68. O.C. 319:1 and 10.
69. Rama, O.C. 319:10. If the water is drinkable for most people but not for a particular person who is extra sensitive or squeamish, that person may not filter the water with a sieve or sifter for himself. Others, however may do it for themselves but not for that particular person; Beiur Halachah 319:10, s.v. ho’ill; Shuchan Shlomo 319:26.
70. Some poskim are hesitant about permitting active carbon granule filters, since the water passes through a filter which contains a sand-like chemical and becomes temporarily unfit to drink, but other poskim are not concerned about it. For a discussion of this matter, see Piskei Teshuvos 319, note 294 and Ohr Yisrael (Torah Journal), vol. 68, pgs. 102-103.
71. Note that some poskim in the USA have ruled that it is permitted, for various reasons, to drink NYC water even without a filter.
72. See Orchos Shabbos 3:39.
73. See Yeshurun, vol. 17, pgs. 535-561.
74. O.C 53, s.v. u’min, quoted in Orchos Rabbeinu, vol. 1 pg. 150. See also Minchas Yitzchak 7:23 and Tzitz Eliezer 14:46. Other poskim disagree with this ruling; see Shevet ha-Levi 1:84
75. See Shemiras Shabbos Kehilchasah 3, note 140 and note 188 and Machazeh Eliyahu 1:51-4.
76. Ramban and Ran, Shabbos 154b. See also Shulchan Aruch ha-Rav 500:18, Chayei Adam 16:8 and Nishmas Adam 5, and Ageli Tal, borer 11.
77. Indeed, as mentioned earlier, several contemporary poskim maintain it is even permitted to drink the copepods-infested water.