Q: Shaikh John, I recently read that water that has been drunk by cat is permissible to do wudu? Is this accurate? Also, why dogs are not considered clean animal but cats are? Jazakallah.
A: You are correct. A pure water source from which a cat has drunk is permissible to use for purification as opposed to a dog. If a dog drinks from a container, not only is the water spoiled but the container must be washed 7 times; one of which must be with pure soil. Allah knows best.
Source: Bidayat al-Abid