I have the same thing with my GH overflow. I was told you have to drill a hole into the 90 at the bulkhead and put some tubing in it. Haven't tried it yet though.
Yes sir he built it, glued it, rodded it, and shipped it. Extra $25, but so worth it. All I had to do was send him photos of setups I liked and he did the hard work.
Ahh so I can at least let it mix my salt for me so thats a plus![]()