My filter xp2 makes a high pitched hum Why?

by James
(Illinois)

I got A used xp2 and went to set it up on my forty gallon long. I assembled it empty to make sure it works ok. I trimed the intake hose but not the out. It sits at ten inches below the water line. At first it was quiet but the next morning it had a high pitch hum. It doesnt appear to have any air in it. It pumps fine. Can I get rid of the noise?? Or is the filter too close to the water level.

 A: I believe your setup is the cause. Specifically, the rotor is running partially dry due to a lack of water up in the rotor/impeller chamber. See the Performance Page in the FAQ section for many Q&A's.