So I am not sure what is happening, but my main flow with the gate valve is just not flowing the way it use to...infact, the overflow is pushing nothing but air and I can hear it. I opened up the main return line ALL the way and place my hands where the water actually flows into my sump (first chamber) and it is not the same flow rate....It is so bad, the backup drain is loud, so I have turn the flow rate of my COR 20 to about 20%....FAR from my usual 55%. I have the Synergy Overflow version 2 1600; on a 120gallon 40gal fuji 36 sump...Suggestions to bring my flow rate back up?