We bought ours new and struggled with slide leaks during the entire warranty period. The driver side bedroom slide was the most frequent leaker. No matter which professional worked on it, there was a different theory and repair, including the now closed factory itself.
A couple years ago, with a soaked rug, I went out in a rain storm and watched. The coach was level, but as luck would have it, a large portion of the water collected on the flat roof found a path to the area above the slide. A stream of rain water flowed off the roof, over the edge and onto the top corner of the slide. Surface tension took over and the flow was directed at the seal that appeared to be tight.
My conclusion was that depending on levelness, rain intensity and wind, the slide seal would occasionally not be up to the task of keeping it dry inside and wet outside. Consider it a design flaw. Maybe the rubber is too hard, it was not installed correctly or the slide itself is not square. Either way, it had not been dependable for our first few years of ownership.
In desperation, I invented two fixes of my own. I bought some rubber "RV Gutter" at Camping world and attached it to the roof in such a way that collected roof water would never again flow down the side near the slide out. After all, Winnebagos, Fleetwoods and our two cheap trailers had gutters! Why not this RV?
The second fix was to create a "dam" against the surface tension causing the water to flow directly against the seal. I bought some nice, thin aluminium strips and glued them to the slide. This may have not been necessary because the gutter prevented almost all of the water from getting there.
In three years, there have been no slide seal leaks! I won!
