I may have mentioned this before but given the importance of the issue, a little redundancy may be a good thing. Why is it important? Because cats are very vulnerable to kidney failure due to lack of hydration. They tend not to drink enough yet this need not be the case. The fact is, cats are not attracted to a still pool of water.
In nature the safest water is moving water that the sun shines on. Still water harbors dangerous bacteria, becomes stagnant and foul so cats are hardwired to seek moving water. They also are attracted to the visual and aural stimulation moving water provides. Almost every time I set up a new fountain for testing in my home Bijou goes straight to it. In this link he is drinking from something I call the Drinkbetter design.