Q. In places like Las Vegas and some counties in California where literally the treated water goes from the toilet to the tap, can you wash netilat yadaim with such water. Even if not contaminated, why should it not be disqualified as water that was used for work (cleaning, washing and drinking from it etc.)?
A. Poskim maintain that if the water was treated and recycled directly into the tap, it would be disqualified for netilas yodaim (Lehoros Nossan 10: 23, Kovetz M’beis Levy 5: 6). However, it is common that the water is reclaimed into a lake, from where it will be extracted for house use.
The above Poskim opine, that since it ends in contact with the ground and is further filtered by it, and then extracted from the underground of the lake, it is considered having gone through a “hamshacha” process, as water for a mikva is transformed by having it run over the ground. This constitutes “ponim chadoshos” or new fresh water and is permitted for netilas yodaim (See Piskei Teshuvos 160: 16: n. 58).
Horav Shlomo Miller’s Shlit’a opinion is similar.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a