If an intrinsic impurity like blood or urine comes into contact with water and changes its smell, colour, or taste, it becomes impure even if it is kurr or flowing water. In fact, based on obligatory precaution, the water also becomes impure even if the smell, colour, or taste of the water changes by means of an impurity that is outside it; for example, an impure carcass that is lying by the side of the water changes the water’s smell.