1) Water which has been used for something is unfit for washing one’s hands. Examples of this include if it has been used to wash the dishes, soak bread or even to cool down a bottle of wine. In all the above cases one may not use this waster for washing one’s hands. (Shulchan Aruch and Mishne Berura 160)
2) Even if the person who used the water is not the owner of the water, the water becomes unfit. (Mishne Berura ibid)
