Thanks. To be more specific, the basket (it has a screw-on lid) does eventually fill with air. I make sure it is tight and the gasket is new and greased. When I shut off the pump, the system drains down fairly fast, with a lot of gurgling. I also notice, when the pump is running at either the hi or lo speed, that the return closest to the pump burps up bubbles on a fairly consistent basis. When I shut everything down, I see no leaks or drips. I am mystified.