We had a cat for years, unfortunately we lost him due to kidney failure, poor cat, we really loved him, but we still have out dog, he's younger than the cat was, and added another dog too. I've never noticed anything getting by the water on mine honestly. And my evidence that it does still capture cat and dog dander is that my dad is allergic to cats and dogs among many other things (I inherited some of his severe and constant allergy problems, and got them a bit worse, thankfully I don't believe pets cause any of mine) and he's mentioned that when I use a Rainbow or other water vac that his allergies stop bothering him soon after I start vacuuming and for a while after, he says its the only time he noticed that his allergy symptoms go away or are reduced by a lot.