I just had this exact issue. Run a garden hose over each valve on the intake side of the pump. You will notice the bubbles in the pump basket disappear. That valve is the culprit. You are taking in a little air. Go on Amazon and by the three O-ring packet (4) sets for $5.99. You will obviously have 3 extra sets for a rainy day. Take a picture of the valve before you disassemble it and at each stage. Remove the 6 or so screws and pull the unit upward. There are two O-rings on the diverter shaft separated by a spacer. Save the spacer. Tere is one larger O-ring on the lid. Replace all three O-rings using a little lubricant. No WD-40! Replace the unit back in the valve and tighten the screws in an opposing pattern. Don't go around in a circle. I am willing to bet the bubbles in the pump and the pool disappear. BTW...if you call in a pool guy they will sell you a new valve for $175 or more plus labor. Trust me this is very easy to do! Good luck.