I own a Westerly Konsort 29. The head is a vacuum model with a single hand pump mounted on the forward bulkhead. There are two Y values: One at the base of the bowl and one at the top of the vent loop. I believe this arrangement allows waste to be pumped overboard (a no-no I know) or into the holding tank, but this would need only one Y valve. I also believe the second value is to empty the tank overboard (a really big no-no). I cannot figure out how to set the values for the three different modes. (1) Flush bowl overboard, (2) Flush bowl to tank, and (3) empty tank overboard. I do know that if I do it wrong, bad things will happen. The valves are labeled "A" (top) and "B" (bottom), and each turns 180 degrees to positions labeled "1" (Left) and "2" (right). Anyone have an answer or suggestion. Of course the manula to this boat is long gone. Thanks!