Just learning the ins and outs of my VS pump. On higher speeds there is no air in pump basket. On extended low speed 1000-1750 rpm there are big bubbles in top of basket. My PB said it s because of the lower speeds I have the pump on. I don't understand the principal. Is that a reasonable explanation or should I be worried about a suction leak. New pool. Water level top of skimmers. Everything working fine otherwise. Pressure normal on filter it seems. Thanks