Originally Posted by Wandering Wes
The pipes are plumbing vents for the kitchen and bathroom and the black "cap" is a satellite radio antenna.
Thank you for your answer. I think the plumbing vents are for the grey/black water tanks.
I agree the "cap" is an antenna but I don't know what for. As far as I know, PW built their last Excel series in 2015 specifically for a rental company. The antenna may be a dedicated GPS antenna for fleet management. That's a hunch. That would make it very useful for me.