Plumbing Vent Caps On Roof --- All Sun Broken & Ruined

Look down inside. On soem RV's the pipe is solid and there are no gaps

on others there is a smaller pipe inside the larger one and gaps between the two where water can enter your walls.

What to do about it

You can basically use most anything as a temporary cap. So long as it is BIGGER than the pipe and you can tape it down without sealing the pipe.