It's a Y not a T. It's SUPPOSED to divert water equally, but because one of the directions is more inline with the incoming hose, most, if not all, of the water goes one direction first. When that tank is full, it then finds its way down the other side of the Y.
I'll get back to you guys about the bilge pumps. The two are amidships under the sole in the engine compartment. I guess it's the lowest point in the boat as all the water collects there. TBH, I don't know where I would put a third. Maybe under the drive shaft in the stuffing box area. Still, don't really have a place to eject it to. Can you Y into an existing above-water thru-hull? Like the one for the sink?
