If a person urinates in a water channel from which people perform ablution, is their ablution valid? Is he to be informed of it? And is he sinful?

The Shaykh : This is 'Abd al-Rahman ibn Talhah al-Zubaydi, or al-Zubaydi, yes. He says: If a person urinates in a water channel from which people perform ablution, is their ablution valid? And is the matter the same if they know about it or if they do not know? ... We have discussed this, my brother. Did we not discuss this, everyone?
The student: Yes.

The Shaykh : Check the tape. As for ritual impurity ... take this as a rule: water does not become ritually impure except by a change in its properties.