I came across another thread while doing some reading and made me curious about the water level in the pump basket. I noticed if I am running the pump at 1750 rpm or higher the pump basket is always full with no air. However if the pump is being run at 1400 or 1600 rpm it will gradually drop the water level in the pump basket over the course of a few hours to about 3" below the lid. Is it normal for it to drop the water level in the pump basket when running at lower rpms?