Hey guys, we just installed out Fafco 4x20' solar heater. The directions say that I should turn the "solar on" handle until I see a 5-7 psi increase . Thing is, no matter what position the handles in the gauge doesn't move, it hovers right at about 4 psi with the pump on the low setting. Any ideas why that might be? I've checked the setup, everythings connected correctly. PSI increases to 20 on the pumps high setting so the gauge is working. Thanks in advance!