Purity: Impurity Ruling When Part of Kurr Water Is Affected by Najāsah

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 17

If an intrinsic impurity like blood comes into contact with water that is more than kurr and changes part of its smell, colour, or taste, in the event that the amount that has not changed is less than kurr, all the water becomes impure. If [the amount that has not changed] is equal to kurr or more, only the amount that has changed its smell, colour, or taste is impure.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)