Originally Posted by Flanny
Those are Air vents - that's why they are right at the top of the tank...
If I had to speculate, I would guess that the top tank is probably not really a "tank" at all, but just a glorified filler neck leading to two hefty hoses (maybe 1" or more) to allow for reasonable fill speeds.
But if the sides are connected to the centre tank (I agree, with a large diameter feeder hose), wouldn't the one breather hose in the centre tank be enough?
(Theory of communicating vessels etc?)