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Topic: Filter, Water, Using on Shabbat

Sharona Shapiro wrote:

Dear Rabbi:

I have never used this forum before but I understand that you give answers to halachic questions. Here is mine: I have a Brita water filter pitcher. Can I refill it on Shabbat and allow the water to go through the filter?

Thank you very much and tizku l'mitzvot.

Dear Sharona Shapiro,

As you know, there are 39 categories of creative activity forbidden on Shabbat. One of them is borer - selecting one type of food or object from a mixture. Pouring wine or water through a cloth in order to strain out sediments or dirt is an example of borer.

But let's say for example you have a full glass of wine, and you only want to drink half. So you pour half back into the bottle. All you've done is to separate 'wine' from 'wine.' This is not an example of borer, since there was no 'mixture' to begin with.

So too in the case of a water filter. Most people looking at a glass of clean tap water see nothing but pure water. Even though we all know it's full of impurities, we accept it and drink it as is. Since we don't view it as a 'mixture' of water and impurities, the impurities are therefore considered part of the liquid itself. It's therefore OK to run it through a water filter.

This is true for most people. However, if you personally would never drink the water without filtering it, then for you the impurities can't be considered part of the liquid; filtering them would be borer. Neither may someone else filter the water for you; but if someone filters water for himself, you may drink it.


  • Shulchan Aruch, Orach Chaim 319:10
  • Ibid. Bi'ur Halacha "Ho'el"

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