What is this? A vent ?

[Drifter66]

I'm working on my Keystone Sprinter 5R I took a cover off inside the bathroom closet. This thing is attached to the Plex plumbing it's not a valve I'm not sure why it's there? I want to run the solar PV wires down this wall before I do I hope someone can tell me what this thing is?

[shootist]

That is the airgap for your tank flush. When the valve sticks open even a tiny bit your coach will smell bad all the time, worse when you flush. Always use a clean hose when hooking up to flush. There are two valves in it. One closes the air gap, the other prevents backflow

[Old-Biscuit]

That is the Anti-siphon vacuum breaker check valve device for your Black Tank Flush System

Water goes in via bottom line...pushes disc up closing off the open slots in top cap and then water flows out the side pipe and down to nozzle in sidewall of Black tank
When you turn water source off the disc drops down allowing air to enter via slots in top cap. This allows water on tank side of Device to drain back into black tank and breaks any siphoning action

Low water pressure (less the 45#) and it can leak ---not enough pressure to push disc/seal
High water pressure (more then 65#) and it can leak---too much pressure pushes past disc

Can leak out top with normal pressures cause they are cheap junk

Clear Plastic and Brass options are available