My water pump has started making noise while pumping. Used to be totally silent.
Still pumps great, but am curious as to why all of a sudden it has started making a moaning and groaning noise.
I can't say that I've ever heard a pump noise described as "moaning and groaning", so this may be of little help to you.
The usual cause of pump noise is either a loose mount (vibrating against the floor or whatever) or insufficient slack in the water line to/from the pump. Those little pumps vibrate a lot and can get a water line really reverberating. These is supposed to be several inches of flexible tubing between the pump and more rigid water lines, but few RV manufacturers do that. I'd try altering the position of the pump while it is running and see if that changes or eliminates the noise.
The other thought that occurs to me is an air pocket trapped somewhere in a water line.