This water filter broke after 1 week. Black stuff from the filter (I'm assuming carbon) was released all throughout the cat water fountain bowl. As a result my cat got sick (terrible vomiting and diarrhea) for several days. Upon replacing the filter with a new one, the same thing happened. In fact every time I replaced the filter, within a week the same thing happened. 
These water filters used to be much higher quality and would last for several weeks before needing to be changed. Im not sure what happened to the quality of this product. I am very disappointed and obviously will not be purchasing again. Other buyers beware!