RichardS
N/A
That's exactly what mine does although mine only has a small volume of air to entrap. I'm surprised that the flow rate is sufficient to blast its way up through a half full version of the OP's strainer and entrap even more air and drag it down the outlet but if yours can do that then it sounds as if low pumping rate might well be the OP's problem.When I start mine with the strainer empty the jet of water from the inlet hits the inside of the lid. This entrains a lot of air into the flow of water and the mixture gets drawn down to the pump. Over a few minutes the ratio of air to water reduces until the strainer is full of water.
Richard