Q. In some countries the city water is not connected directly to the taps, but is stored first in a water tank usually at the roof of the house. To avoid spilling the water once the tank is full, the water pushes up a floater that turn off the valve for incoming water, (similar to a common toilet). Why is that water not considered as having done work, since it turned off the valve and therefore should not be fit for netilat yadaim?
A. Horav Shlomo Miller Shlit'a explained that the water only caused that no more of it should enter the tank; avoiding doing work is not work. Dovev Meishorim (4: Likutei Teshuvos: 20) adds to the above reason the following two.
1) Only the very last top layer of incoming water that pressed directly on the floater performed work. The other layers of water below are only creating a gromo or an indirect work for achieving the valve closing, and that will not disqualify those waters. Then, the top layer will become annulled on the majority of waters bellow via bitul berov, and all the water will become permitted.
2) The work was done by water that was attached via the still open valve, to the water source. As mentioned above and in Shulchan Aruch (O.H. 160: 5) a mikva or a spring are not disqualified by this kind of water. See also Chashukei Chemed (Chulin 66a) that adds another three reasons.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit'a
Important Numbers
