Shaykh Ibn ʿUthaymīn said [concerning water to which something pure is added causing the water to change one or all its properties from taste, smell, and colour]:
“This is not enough to change this water to a state which makes it ineligible for wuḍūʿ, except if the additive is sufficient to completely change the way we refer to that water. For example [to the point] where we would say: ‘this is gravy’ or ‘coffee’ [despite those things being primarily water-based]. At such a point, these liquids stop being referred to as water, instead they are termed beverages whose respective names are derived from the additive mixed with the water. This is the opinion taken by Shaykh al-Islām Ibn Taymiyyah. The evidence as to the fragility of the argument [that anything pure that changes water makes it ineligible for wuḍūʿ] is that they will also say that if tree leaves were to fall in water and change it, this water is amenable to ablution due to the difficulty of preserving the water from such things. However, if a person was to intentionally place [the same leaves] into the same water it would be considered ineligible for wuḍūʿ.
It is well known that if the ruling of the water [actually] changes in conjunction with some factor, it should make no difference if that factor is hard to preserve the water from or not, or if that factor is placed intentionally or otherwise.
Likewise with regards to water that is changed by that which is najs [impure]. There would be no difference between the najs that is hard to avoid and that which is not, or that which was placed intentionally or otherwise. As long as the reason for the ruling is the changing of the water itself.”
Source: Al-Sharḥ al-Mumtiʿ 1:47-48
Translated by: Riyāḍ al-Kanadī