Why won't my pool pump strainer fill completely?

I have a Hayward Power Flo Matrix 1-HP Pool pump that is hooked up to an above ground pool. I have read that the strainer should be filled completely with water while the pump is running. No matter what I do, I can not get the strainer to fill completely with water, there is always at least an inch of air on top. How do I go about filling the strainer completely?