From the looks of your attached photo, you need a black water and gray water elbow valve for your trailer. The closest thing we have for the setup is the Bristol Double RV Waste Valves - Elbow - Rotating - 3" Spigot and 1.5" Hub to 3" Lug # 34466ND13BAR. This part comes with a 3" waste water valve and a 1-1/2" gray water valve. I recommend making sure that these valve diameters are compatible with your setup. The valve handles rotate so you can set them to an easy point of access.
I went... view full answer...