Kosher or Not Kosher is beside the point - this is just yucky.

There's Something in the Water, and It May Not Be Strictly Kosher

These rabbis have recently discovered that there are tiny creatures, called copepods, in the unfiltered water that streams into the city from upstate. These tiny organisms are harmless. But they are crustaceans. And crustaceans are not considered kosher.

So, the Orthodox are starting to buy water filters en masse. Except those that have lights.

"Some of the filters have a light indicator; the light goes on, it's no good for Shabbos," Mr. Tuht said. "I work here, I sell stuff. You learn."