Aloha. Here's my new system. I've got a 160 gal FT with a 90 gal GB filled with lava cinder above. I'm running a 350 gph pump continuously. The plumbing is a 1/2" from the pump and a 1 1/4" standpipe witha 2" bell. I found that witha 1" drain, the GB took 30 minutes to fill/drain. With a 1 1/4" drain, I could fill/drain the GB in about 8 minutes.
[video:e41umy9c]http://www.youtube.com/watch?v=PcfhcwUHO1o[/video:e41umy9c]