Replaced old 2HP with Pentair VSP. FAFCO Solar. As I start to use solar, getting bubbles thru returns. The amount of bubbles is proportional to the RPM of the VSP. (2200RPM = lots of air, 2300 = less air, 2400RPM and above - champaign bubbles. At 2400RPM PSI is 16. I Replaced VRV. Cleaned DE...