Combining Black and Gray Roof Vents for 1958

[mello mike]

This to me is a odd design. On my '58 Overlander, the black and gray roof vents are about 18 inches away. Why didn't they just combine them? I would think that joining the black vent pipe to the gray pipe up high near the roof would prevent odors/gases from traveling throughout the gray piping and into the trailer. Has anybody else combined these vents into one? Another benefit of combining these would be the elimination of one roof vent and another source of leaks.

[tkasten]

This is just a guess - might have something to do with codes?

[cameront120]

Showers, sinks and toilets all connect to a main stack vent (usually 3") in modern home construction, so it isn't a modern code issue. My service manual for 1979 models shows combined grey and black tank venting, so it is done on newer models. I think if you were to bridge the two with a crossover high enough to prevent cross- contamination, you'd be okay.

[Grand Master]

58's didn't have gray tanks. Perhaps yours was added in recent years and they just vented it the easiest way possible.

[mello mike]

Originally Posted by Grand Master

58's didn't have gray tanks. Perhaps yours was added in recent years and they just vented it the easiest way possible.

Correct. No gray tank, but there is venting for the gray system.

[azflycaster]

The grey vent is most likely a vacuum break. It prevents the flow of water going through the pipe from siphoning the water out of the P-Trap. On my trailer the vacuum break for the sink as well as the vents for the grey and black tanks attach to the same vent pipe in the rear of my trailer. There is a separate vent pipe for the vacuum break for the kitchen sinks.