There is only one vent off of the main tank. Basically you are just inserting a header tank between the engine and the main tank. On the main tank, the vent is open (or a check valve, whichever way you want). The clunk line from the main tank goes to the vent of the header, then the clunk line of the header tank goes to the engine. There are no more open lines with this system than there would be with just a main tank.

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