Help in identifying this device on motorhome roof

[DKRITTER]

Auugaaa

 

[Bob K4TAX]

We have had our Renegade Villagio since 2015 but learn something new about it every year - for the better. The device shown in the photo has us stumped as to what it is. Does anyone know? Thank you.

That is a venturi tank vent. Can be used on both the black water and grey water vents. I guess they work, never needed to use one. The standard cap-over-vent pipes seem to work well It is a standard PVC plumbing T with 3 different size openings. The smaller opening faces forward.