[DON]

Most local plumbing codes require a vent within 10′ of a trap. Most of our drains are wqithin 10′ of the waste tank, so the roof vent works. I have blocked vents on several coaches with no difference in operation.

I knoiw we do not have to meet sticks and bricks codes, but it gives one an idea of what works.

[Gerald]

Mikee

thanks for the inputs. I will most likely isolate the air admittance line and cap it off from below. I shall remove the T and just connect the shower p trap line to the grey tank via a 90. since there are no other lines draining on that line, i should be fine.