The ruling on flowing water mixed with impurity

Question:
Is there a distinction between a small amount of water and a large amount?

Answer:
As mentioned earlier, a small amount is defined by custom, such as a qullah or two. If impurity falls into it, it must be poured out. As for a large amount by custom, such as a qullah, two qullahs, or what is around that, it is not permissible to pour it out due to the cause of change. As for two qullahs, this is based on the mentioned text. As for what is less than that, the ruling is the same, based on the saying of the Messenger of Allah (peace and blessings be upon him) However, if it is a small amount, it must be poured out, based on the hadith: "If a dog drinks from a vessel, let one of you wash it seven times." This indicates that a small amount of water must be poured out, because it is generally affected, like the water in small vessels. Yes.