When my spa/return selector is set to any position less than full spa the strainer pot shows lots of air, and the pressure stays around 20 pounds. Bubbles are present at one spa jet and two returns out of five. The air is only in jets closest to the pump. When I select full spa pressure the waterfall into the pool goes full blast and the pump jumps to 35 pounds of pressure, the bubbles immediately stop.
My pool is 15k gallon, and the pump is a PacFab Challenger DE filter. There is a backup pump for the pool sweep. Both pumps are leaking water at the front seals. Air is also pushed through the pool sweep lines when it is on. I have two front seals coming and will replace this weekend. I have lots of experience replacing seals after 22 years of owning this pool!
So, why would I have several air leaks on shared or full return selection, but no bubbles on full spa selection?