Ricardo18
New member
How much water is in your overflow boxes? With return pump off, they should empty in seconds...
You are right..They are extra large, probably2 gallons each and they do empty in seconds because the full siphon is still operating even though the return pump is off.
Now that I think of it; I have a check valve at my return pump which stops the return lines from siphoning...so I don't see the necessity of Mark's check valve thing.