Rooftop vents
 

I decided to order 360 siphon vent caps. I have a black, and two gray tanks so right I ordered 3. Much to my surprise I got up on the roof to install them and there are 4! Maybe one is for the washer drain to vent? (my best guess)
:facepalm:

There are "attic vents" up there as well that look the same except my attic ones are white.

Mark

Attic vents are normally the mushroom vents, larger. One in front, one in back.

My attic vents are much larger diameter than my waste tank vents. All are white.

I have 2 mushroom vents, one in front a rear center. There are 4 other vents. They are all the cap style for tank vents. One is positioned about where the washer drain is. I think it may be a vent for the washer drain. Maybe someone knows for sure.
https://instagram.com/p/BVyAJ8XAwgN/