Safe to drink - but is it kosher?

Yet for the more orthodox among them, Gotham has become less congenial. Its water may not be kosher.

Tiny organisms known as copepods have been found in New York's unfiltered tap water. They are harmless.

The problem is, they are crustaceans. And eating crustaceans - shrimp, crabs, or any other creature with an external shell - is against Jewish law.

Following the discovery of copepods in the water last month, there has been debate within New York's Orthodox Jewish community.

"The question is, is it an organism that is independent of the water, or is it an organism that is an extension of the water," Mordechai Pupko, an Orthodox rabbi in Brooklyn, told BBC News Online.

Rush

If copepods are regarded as foreign organisms, they are not kosher.

If, on the other hand, they are viewed as consubstantial with the water - like, say bacteria - there is no problem.

Some rabbis have already warned the faithful against drinking unfiltered water.

According to the New York Times, some of New York's hardware stores have experienced a "rush on water filters".

But many orthodox Jews are not bothered about the copepods swimming down their pipes.

Rabbi Pupko told BBC News Online he was not aware of any member of his congregation rushing to buy water filters.