I have air bubbles in the return line to the pool. There are no air bubbles in the skimmer at the pump. There are no visible leaks anywhere. I took apart the top valve and cleaned it and soaped all the o-rings. put it back on and No bubbles. Today I cleaned and vacuumed the pool, backwashed the filtier, and no have air bubbles again. I took the valve apart again, cleaned and soaped it but this time did not fix the problem. My guess is that it is time for a new top valve. All chemical levels are good and otherwise the water is clear. Just hazy from air bubbles.