Originally Posted by
TriadDawg
If you look again, at least at Birdman's design of this filter, you will see that the outlet to waste is BELOW the pond return. Also, be sure the manifold is expelling bubbles across as broad an area of the barrel width as possible. I would worry that the air manifold would not efficiently clean the gravel media if it is tight against the first layer of gravel.
I would keep the air manifold under the gravel tray, and plumb the 2" shower drain for your Line-In from pond. If you want a clean out, just install a second shower drain with valve to waste.
I think your current Line-In up high on the barrel is increasing head pressure on the pump, but maybe you need it this way for physical and space limitations.....