We purchased an 1960
18' Traveler, CA manufacture with the Head in rear street side corner. The Traveler was gutted inside by a previous owner, having only the fresh water and black water tanks. We need help identifying the three connections on the top of the black water tank. All connections, including the one on the bottom to dump the tank have been pluggged with screw in or expansion plugs. The smaller conection, about 1 3/4", is the black water tank vent which must elbow to near the wall and go out through the hole in the roof. I am confused by the two large plugged openings on top of the tank since I believe it had a toilet only and no shower; a larger hole, ~4", closest to the back corner of the trailer and a second hole, ~3", farther out. I have attached a picture that may be worth more than my explanation.
I also don't understand why the grey water connection was plumbed to the outlet pipe below the blackwater tank rather than into the tank since it would require grey water to backup into the tank. It may be that there once was a separate grey water outlet but it was removed since a previous owner had the idea of converting the trailer to a makeup room or cabana and connected to land plumbing.