(I am assuming you have an HOB) As Davy suggests, take the entire thing apart, impeller and all, clean all (some require a little scrubbing) this type of cleaning should be done atleast annually to keep parts in good repair and ensure a long life. Make sure that the impeller is securely in place and all parts are properly put back. This is vital. You should be able to move the impeller on the shaft before putting it back in. If it doesn't move then play with it a while. It's pretty hard to brake something just by cleaning it. Good luck...