Here is my closed loop that is hooked up to 2 Seaswirls 1" models all plumbing is 1.5"...I have approximately 12' of head both units are driven by a Dolphin Ampmaster 3000....Help me out here guys....I thought I would get atleast 2000GPH for both of the SS's (1000 ea.) but after calculating I think im only gonna get about 1400 maybe a tad less even...all thoughts opinions, and tips appreciated....I havent glued it all together yet.