Filtering Copepods on Shabbos

Q. New York City water is unfiltered and can contain copepods (small crustaceans). Some poskim allow drinking New York City water as is (for reasons beyond the scope of this Halacha Yomis), while others maintain that New York City water must be filtered. I live in New York City and follow the stringent opinion. Am I permitted to filter my water on Shabbos to remove the copepods?

A. The Chayei Adam (Nishmas Adam 16:5) discusses whether filtering wine or juice to remove insects is permissible on Shabbos. He is uncertain if such filtration constitutes borer (separating the good from the bad) which is forbidden on Shabbos. On the one hand, from a taste perspective the liquid is potable, and a non-Jew will drink the liquid as is. On the other hand, as Jews we cannot drink the liquid with the insects for halachic reasons. Are tiny insect (which do not affect the taste but present a halachic restriction) viewed as pesoles (a bad part of the food)? Do we compare this to filtering drinkable water to remove small particles, which is permissible, or do we say that filtering small insects is borer because of the halachic restrictions? The Chayei Adam leaves this question unresolved. Since the question at hand is one of a Torah prohibition, we must be strict, and we cannot allow filtering copepods on Shabbos for those individuals who consider them forbidden. (Built in faucet filters will be discussed in an upcoming Halacha Yomis.)


The Gerald & Karin Feldhamer OU Kosher Halacha Yomis is dedicated to the memory of Rav Yisroel Belsky, zt"l, who served as halachic consultant for OU Kosher for more than 28 years; many of the responses in Halacha Yomis are based on the rulings of Rabbi Belsky. Subscribe to the Halacha Yomis daily email here.