Hot water loop, with circulation pump. I suspect the noise is air in the impeller, but I'm not 100% sure. Before I send this pump back for warranty replacement, I'd like your opinion on whether or not its actually a bad pump, or, as I suspect, cavitation. The pump is located at the end of the loop as it returns to the water heater through the drain port. There is no air vent installed in front of the pump even though the installation instructions recommend one. Pump was installed by the builder's plumbing contractor.

Video showing the pump, and the noise it is making:
https://youtu.be/4pQYyKVyQGc

 

Welcome to the forums.

Sounds like a bad pump to me.

 

Thanks Pete, for the welcome, and the answer