Plumbing question re: dual overflows & sump

[phishcrazee]

<a href=showthread.php?s=&postid=14269736#post14269736 target=_blank>Originally posted</a> by sgarrett1108
couldn'y you feed the skimmer with directly via the drain and then empty into the first chamber. Yould would be getting the dirtiest water and wouldn't need a pump to feed the skimmer.

How would I know the gph flow into the skimmer though? A mag 12 is recommended for it; would the flow be 1200 gph?!