Waste Cap vent?

[danm1]

I seem to get frequent blockages in my holding tank vent despite running a hose into the fitting when I can. I suspect poor design but the area is very hard to reach, so I have been dreaming up alternatives that don't require contortions. Is there any point in modifying a deck cap for the pumpout with a second vent, or would the value be instantly negated when the bottom of the pipe is under fluids?

 

[Dalliance]

…….. instantly negated when the bottom of the pipe is under fluids?

Assuming your tank is correctly plumbed (Vent and inlet from the head near the top of the tank and outlet at or near the bottom.), I think you’ve identified the primary flaw in your idea of adding a second vent at the waste deck cap.