Help- Issue with WB Downpipe

[Lizbeli]

Hey guys, this is my like seventh tank and second waterbox. My previous waterbox was whisper quiet. But this time I plumbed in a fleece roller.


Issue- water level starts off correct in the overflow box. Full siphon, no air getting pulled in from the top. However, you can hear air inside the downpipe. When it gurgles, water will come down the emergency drain. I can’t tell if its trapped air or maybe my plumbing of the reefmat isn’t air tight.

I have tried opening the drain all the way and increasing pump speed, but it seems to have trouble keeping up with speed 1 on a varios 2. I have tried closing it in hopes more water pressure will purge the air in the down pipe.

I am at a loss and have never had trouble like this. Due to plumbing in a reef mat for the first time- I want to blame it on poor seal and air getting sucking in down there. But idk..

 

[Lizbeli]

Well.. of course after it running for hours it finally decided to quiet down after I posted this.

However even with the gate valve all the way open, and the pump on setting #1, I still get random trickling of the emergency drain.