air bubble in pump basket

[mbar]

We replaced the pump this year with a 3/4 horse power hayward tristar pump. There doesn't seem to be any air coming back into the pool through the skimmers, but there is a bubble in the pump basket. When the basket is taken out, the bubble goes down to nothing. The basket does not come up high enough to break the seal, so I am at a loss as to what it could be. There is sufficient pressure, which is another baffling matter. Does anyone have any experience with this? My husband thinks that the basket is too thick to let the air bubble out - but i am not sure, because when I called Hayward they said there should not be any air in the pump basket.