PNW! WA is my home state.
I do have a small hole drilled in the secondary pipe.
I've tried removing the main drain "U" but with no luck. I'm pretty I didn't glue that sucker in there but it's not coming out. I'm thinking when I glued in the under side some of the glue pushed up and cemented the "U" side plumbing. Not too happy about that.
also wondering, are the overflow and return pipe the same size? They look pretty close in size. If they're the same, or even 1" vs 3/4", it's possible that two 3/4" return line in full capacity is over the overflow capacity of a 1". The actual capacity of the overflow pipe is smaller than the same size as return pipe, because return pipe has the return pump to add additional head pressure.