[outrigger]

On my 42, First you open the seacock in the aft bilge.
Second, turn the y valve which is located under the cabin floor just forward of the holding tank, make sure the arrows are pointing to the hose going to the bottom of the tank, and the other pointing to the hose going to the over board discharge pump. This pump is located on the port side of the engine room just under the big air vents in the hull. then hit the switch on the DC panel, you should then start to see bubbles come up from the underside of the boat, on my aft port corner.