What is this part of my plumbing?
Can anyone tell me what this black part is in my bathroom plumbing system. It has a supply hose rising up to it then has a hose going back down into belly of trailer. It also has a directional flow arrow on it. Just curious as to what it is, it's not giving me any grief, but I just want to know what it is.
2011 GMC Sierra 2500HD
2014 Rockwood 8289WS, Diamond Pkg.