You have an air leak in the suction side. hopefully not your new piping....try regreasing the pump basket lid then put it back on if that doesnt work then turn the lid slowly like your going to take it off again BUT DONT take it off -do so with the pump off ofcourse. The small amount u are opening the pump lid will allow just enough air in to create vacuum and slowly fill that basket to the top without the bubble. Then it should run without any turbulence. as far as i know you shouldnt be able to see any bubbles or turbulence through that pump lid or you have issues of some sort.