Got my sump running, I used high quality gate valves but I am having a hell of a time adjusting the two herbies to equal out. I read about this potantial problem with dual herbies. I will get them adjusted so my EM drain starts to have some flow - I close one or the other valves off as small as I possibly can adjust. The result is that overflow drops to below the strainer - sucking air and being loud. I turn it so small - probably 1/64 of a rotation, if that even. I did not want to drill more holes in the tank for a balance tube and wanted dual herbies for flow, argh, frustrating, I'm not sure what to do.