What is the ruling on mixing water used to remove impurity before and after the place is purified?

Primary text

If water used to remove impurity before the place is cleansed mixes with water used after the place is purified in a single container, and the total volume is less than two Qullahs (a specific volume), the entire mixture is impure, regardless of whether the water changed in appearance or not. The proof is that impure water mixed with pure water, being a small quantity, results in the mixture being impure, just as if it mixed with water unrelated to the washing process.