Return Bulkhead so deep?

[Squiddy]

I had no idea Mike customizes the tanks.. I assumed it came from the factory like this. I will definitely need to take the standpipe out and cut it down I guess. I supposed I wouldn't have to glue the coupler on when I join it back together would I? If I left it unglued, then I have the ability to adjust the length at any time.

I had thought about putting a check valve inline with the return but have heard that they do fail and so I'd rather fix it at the output. Would locline seal enough to prevent water from seeping back down the return line? Or would I have to put solid PVC up to the surface and then run locline from there?

I have been only turning on the return pump when I get home from work in the evenings because I'm scared something is going to go wrong. I'm glad I put that ball valve in there.