Answer: First things first: the Lucky-Kitty Drinking Fountain for Cats is designed to run virtually noise-free, so if it’s humming noticeably there’s something wrong. Check the pump by putting it in your sink and letting a small amount of water flow into it - if the pump doesn’t make a humming noise the problem can only be one of the following:
Check whether the pump is securely positioned - usually the problem is that the pump’s feet have become dislodged from the base of the dish, and so the pump’s coming into direct contact with the ceramic. All you need do is firmly press down the rubber feet - you could also rub a little alcohol into the feet and inner dish to enhance adhesion - and your fountain should be as quiet as it was on the very first day.
If the problem persists, it could be that the upper section of the basin has not been fitted properly to the lower section - simply readjust and the noise should disappear.
If that doesn’t help, then it’s highly likely that the housing of the pump’s rotor is dirty. Please clean the pump thoroughly as described in the instructions and remove the small propeller from its housing. Also remove the connecting piece where the tube is inserted into the pump and clean the opening. In 99% of cases, the noise is due to a build-up of debris in the housing, which disrupts the smooth flow of the magnetic impeller. We recommend that you clean the pump thoroughly once a week, as illustrated in the instructions.