I have a badly stopped up passenger (right) side cowl drain. Accessing the tube from the top there is no debris. It must all be towards the bottom of the tube. I want to get to the exposed bottom end of this tube to try and reem out from that side. What has to be removed to gain access to this end of the tube? THX.

 

They exit in the rocker panels below door level
pretty much lined up vertically with the cowl.

 

You will have to remove the rear of the wheel well liner, then you will see the windshield washer reservoir.
I have done this twice to remove the reservoir, I cannot remember if the hose is visible with the reservoir in position, sorry.
There was quite a collection of dirt and debris washed down the tube, I clean it all out and sprayed Fluid Film in the area. The tube should be made longer by fitting a larger tube on it.
I’ll add a PDF to show the reservoir removal. CLICK

 

Thank You. Yep it was under there.