Originally Posted by hot rod
My Pace trailer is exactly the same way. My problem is at the rear, the roof sheet metal seems to flex vs. the aluminum perimeter trim eventually cracking every kind of sealer I have tried. I like your drain idea. That would work in the problem area of my trailer. I'm looking forward to see how you did it where the drain is flush enough to drain everything. Good idea!
Next time up there (next weekend) I will take a few photos of the drain......for now the quick explanation.....everything is 1-1/2" PVC SCH 40..... I used a shower/tub drain, I removed trim cover, the actual drain thickness that sits on the roof is about 1/16" the drain bottom fits nicely into the inside of the 1-1/2" PVC, I ran a bead of PL adhesive before twisting it into the PVC. So at this point I have the drain set into the PVC pipe, total length about 14". Drilled a 1-1/2" hole through the roof, I drilled two small 1/16" holes through the face of the drain, ran a bead of dicor self leveling caulk around the underside of the drain, set into roof, use two screws to fasten drain from top, caulk oozes out....one 90 degree elbow inside the trailer , line up the hole in the sidewall, drill another 1-1/2" hole in the sidewall, send a piece in from the outside, connect to elbow. From the inside use a stainless collar to finish the look of the pipe going through the wall. On the exterior run a bead of caulk around the pipe as it exits the trailer, there should be about 1" protruding....to finish the exterior you can add another collar or in boating stores they make a clamshell cover that can go over the pipe and conceal it at the same time...again I will follow up with photos....Finish with a bead of self leveling around the drain on the roof covering the two screws....Gene.