Q. I own a water powered motor that I use to open and close the suka roof on Shabbath and Yom Tov. The water used is not wasted, it ends in a pool that we use as a mikva for men, (it is connected to a rainwater bor). Since the water performed work, (moved the motor), is that mikva kasher?
A. Shulchan Aruch (O.H. 160: 2) rules that water that was used for performing work (melacha) is disqualified for netilas yodaim, (washing hands for eating bread). The reason that most Poskim quote, is that once the water was used for any kind of work, it is usually discarded and considered unwanted, and therefore unfit for the mitzva. (Mishna Berura ibid. 6).
Horav Shlomo Miller’s Shlit’a opinion is that indeed, this water would be disqualified for netilas yodaim use.
However, Shulchan Aruch (ibid. 5) maintains that this type of water does not disqualify a mikva or a spring, as long as the water is attached to it, and one can also immerse one’s hands in the mikva and comply with netilas yodaim.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a