Tim, it's looking really good. Please explain how and or why the check valve works best for your set up. From what I understand a check valve is a false security, it isn't if it fails but when. There should only be enough water in any given system so that when the power is off the sump will hold all the water that comes down from the display tank and from the plumbing. You can even give yourself a few inches of cushion in that area.
My sump still has plenty of room when the power is off for at least five more gallons. I could have built it different so that it didn't have that much extra room but I have such a big volume of water already I wasn't worried about five gallons or so.
:wave: