Q. Re - question 2987 above. I meant to ask on a water purification plant that prepares and serves the water to our community.
I became aware that often the workers may eat their lunch or snacks close to the water tanks, and it is likely that some crumbs of chometz could fall into the treatment tanks during Pesach. Since the water is constantly collected, treated and pumped into the system, it is not kept the twenty-four hours required for kobush and the only concern is eating the small particles of chometz themselves.
That is why there is questioning on the size of "Mashehu." Since if it applies to a particle that could be seen by the eye only, people on their homes during Pesach could filter their water, and avoid eating those particles.
A. Indeed, in the case you described, since there was no issue of "nosen ta'am," (the flavor imparted by the prohibited substance), as the prohibited chometz was not kept in the water tank for twenty-four hours to be considered "kobush" or similar to cooked, and able to impart flavor or taste, the only prohibited component would be the particle itself. As noted above, it has to be visible enough to be noticed by an ordinary eye.
Therefore, we can indeed assume that it could be easily be filtered by commonly used water filters.
In a similar case, one should indeed filter the tap water one uses during Pesach.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit'a
Important Numbers
