To the video on youtube:
Evidence for water mixed with impure substance which does not change the characteristics of the water:
"[...] provided that water is still in its original state, mixed with nothing else, it is deemed pure as scholars uniformly agree. They also agree that if any of its three basic characteristics - odor, taste, and color - change due to any impure object, then water is deemed impure and it is impermissible to use it as a means of purification. Yet, some scholars differ regarding the purity of water when any of its characteristics has changed due to a pure object - such as tree leaves (like lote tree leaves), soap, potash, or suchlike pure materials - provided that such a material is not predominant in the resulting mixture. In fact, the sound opinion is that the resulting water is still deemed pure, and it is permissible to use it as a means of purification from both ritual and tangible impurity.
Due to the above, we can state that water is divided into two categories:
1 - Pure water, which can be used as a purifier, whether it is in its original state, or mixed with a pure object provided it is not prevalent enough to change the composition of water or turn it into another object.
2. Impure water, which cannot be used for purification from either ritual or tangible impurity. It is also the water of any of whose characteristics (odor, taste, or color) has changed due to an impure object. And Allah, the Exalted be He, knows best."
(source: A Summary of Islamic Jurisprudence, vol. 1 (2005), by Shaykh al-Fawzan, p. 12)