Herbie drain is a pain

[Potatohead]

Originally Posted by Ryanerickson

I had this issue turned out there was shells in my return pump causing inconstant flow. Are you using a gate valve to controller it ?

I have a gate valve on the drain but nothing on the return. I thought that it could be varying return flow, it's possible, but it seems to me in that case the overflow level would go both up and down, not just up... But I could be wrong. I may add a ball valve on the outlet of the pump just to eliminate that possibility.