I have bought a 2005 Gulfstream and am unable to discharge the head overboard. I have what appears to be a dual system with y valve and sea cock for over board pump out. The manual says I should have a head pump out switch but I only have a switch for the macerator. In the manual the macerator and pump appear to be one unit so I presumed this switch would do both. I can hear the pump and the y valve and sea cock are in the proper positions but the fluid level doesn't change. We suctioned out the system and with very little use I see liquid in the toilet. Is this normal? I am wondering if I could have a blockage or if the pump may be broken? Any helpful thoughts?