Okay well if there isn't anything hindering the flow I would build a new one out of 1". Have 2 pipes be 9" long, 1 pipe that is 6-8" long(which is determined by where you want the waterline) might as well start it long and then cut it down afterward to where you want it, 1 pipe 3" long, 4 pipes that are 1-1.5" long, 7 90's, 1 T, and then a length of pipe to get to your sump.
1. Put it together with the 6-8" pipe and 1 of the 9" pipes with a 90 at the bottom of each then use a 1-1.5" pipe to connect them in a U shape and that is the piece inside the tank.
2. Put 2 90's together with a 1-1.5" pipe and attach one of the 90's to the 9" length of pipe from the U you just built.
3. Put 2 90's together a 1-1.5" long pipe and attach the last 9" pipe and the 3" pipe. Put the T on the 3" pipe and the connect the 9" pipe to other 90 that you just added to the U shape.
4. Put the last 1-1.5" pipe to the last 90 and attach it to the T and then you are ready to add the length of pipe to get the water to the sump.
There is no need to glue it just push the pieces together really hard. It isn't under pressure so it will not leak. Don't mess with those 90's that you added to the intake. We just need to get you up and running.
I also do not use air check valves as I have the clear tubing so I can see if air is collecting.
I did a rough sketch in MS Paint of how I prime mine. Since it isn't glued together you can turn the pieces to make this shape.
Then pour water in the intake until it fills the pipe and starts to come out of the T. Then you rotate the pieces to make it the overflow shape and it should hold the water and there shouldn't be any air inside.