After Hurricane Katrina, I purchased a new 16' Haulmark trailer. The trailer has been great, but black streaks and water stains running down the side of the trailer has been a problem. The only product that I have found that can really remove the stains is Flitz metal polish. I am in the process of finding something better, but until then, it's going to take a little extra elbow grease to keep this trailer clean. The other option that I found is to install EZE RV Gutters. This stull apparently stops leaks and streaks. I have ordered this product and will let you all know how well it works or not. Their Website ishttp://www.rvgutters.com/ Hope this helps.