Between the pump and the sac on the fill line. Typically, everyone back when listing was the thing to do would cross drain. with running slightly flatter nowadays I'm not sure it would make as much of a difference. However, even with a gate I run slightly listed as I believe you get a nicer cleaner wave with out "the line" through it. Even with mine cross drained water still pours out while running so I just bought some rubber corks to start sticking in the thru hulls on the side of the boat.