Hawzah News Agency – Based on Ayatollah Sistani's risalah:

- Water that was pure and it is not known whether it has become impure or not is pure. And water that was impure and it is not known whether it has become pure or not is impure.

- If it is not known whether some water is unmixed or mixed, or whether it was previously unmixed or mixed, then such water does not purify an impure object, and wuḍūʾ and ghusl performed with it are invalid.

Source: https://www.sistani.org