When I have my spa in spillover mode where it's spilling into the pool, I am getting lots of bubbles coming from all of the jet's. There are not as many bubbles as when it's in spa mode but its close. My spa pulls in the air through a curved pipe near the spa using venturi action. While my spa is in spillover mode, I can put my hand over this pipe and the bubbles stop. Is the normal? Should this venturi suction be occurring when in spillover mode? If not, what could be the issue?