Purity: Ruling on Waste Water (Ghusālah) from Washing Impure Objects with Qalīl Water
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 25
Qalīl water that separates from an impure object by itself or as a result of pressure and suchlike when that object is washed or after it has been washed is called ‘waste water’ (ghusālah) and is impure (najis). If before pouring water onto the object that had become impure there was no intrinsic impurity on it, the impurity (najāsah) of the waste water is based on obligatory precaution. There is no difference if that object is from among those things that becomes pure by washing once1 or by washing more than once. If the object is from among those things that must be washed more than once, there is no difference if the waste water is from the final wash or before the final wash.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)
Such as the impure inside of a utensil. See Ruling 144.