NYC Water

October 12, 2004

The following statement is not meant as a Psak for individuals or communities. Rather it is a statement of OU policy for the restaurants and caterers under its supervision during this interim period while research is still ongoing.


While we share this with the public, we recommend that you speak to your Orthodox Rabbi for his guidance in this, as in all Halachic matters.

Tiny crustaceans called copepods have been found in New York City tap water. The species we are finding primarily is Diacyclops thomasi, along with some Mesocyclops edax and Skistodiaptomus pygmaeus. These tiny crustaceans are ubiquitous in ponds, lakes, and reservoirs. New York City, because of the high quality of its water, is not required by the EPA to mechanically filter its water. Their appearance in tap water as small white specks may represent a significant kashrus issue.

It is important to note that in some cases, water containing aquatic micro-fauna is permitted for consumption by Halacha. This is determined by several factors, including:

• Whether or not the organisms came into existence in water contained by vessels, cisterns, wells or still-water enclosures, and other factors (See Talmud Bavli: Chullin 67a, and Shulchan Aruch: Yoreh De’ah: 84:1,2 with commentaries);
• The visibility of the organism to the unaided eye;
• The frequency in which the organisms appear in the water from the tap.

Some Poskim (rabbinic decisors) believe that one of the above considerations might apply in our case, and rule, therefore, leniently. Many others feel that the prevalence, nature of the water source, and size of the copepods do not allow for a lenient decision. Since this is an issue of a potential Issur d’oraisa (prohibition on a biblical level), we are issuing the following, interim, guidelines to OU certified restaurants and caterers.

• Tap water in New York City (i.e., the boroughs of Manhattan, Brooklyn, Queens, Bronx and Staten Island) should be filtered before drinking;
• Products already manufactured may be used, even if made with unfiltered water;
• The water supply of dishwashers does not require filtering. Similarly, dishes may be washed by hand in unfiltered water if the dishes are subsequently towel dried, or left to drip-dry without “puddles” of water in them;
• Water should not be filtered on Shabbat or Yom Tov because of the prohibition of borer (selection). Rather, filtering should be done before Shabbat and the water should be stored for Shabbat use. One may, however, filter water for non-food purposes on Shabbat and Yom Tov.
• Bottled water is permitted for use.

We have found filters rated at 50 microns to be sufficient. Most commercial filters are finer (10-15 microns) and will filter out the copepods. Filters must be maintained or they lose their effectiveness.

The OU continues to evaluate the issues. As new information emerges we will make it available to the public. As in all such cases, individuals should consult with their local Orthodox Rabbi for guidance.

The OU Fact Sheet on Water


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