A trial fit of the manifold
The upper two valves on the right are for the front and rear main ballast tanks. The lower right black valve is an on/off for the supply line. The lower middle valve is the air supply for the variable ballast tank. The middle valve on the left is the shut-off/vent valve for the variable ballast tank. The upper left red valve is the emergency shutoff valve for the plumbing thru-hull.