This blurry picture shows my one of the Grundfos pumps being plumbed into to the "U" arrangement.
Both pumps being plumbed into the 2 existing T's that pull from the bottom of the tank.
Attaching a mending plate to the tank lid. There is a sheet of plywood underneath the XPS that the plate is screwed into. The mending plate will be later have a theaded rod through it from the tank edge to secure the lid down.
The two return lines being installed into the lid. They only go past the bottom of the lid a couple inches, so they are far above water line. This ensures air can enter the line during drainback.