Try buying your stainless steel clamps from a boating center. They are the same price, and the screw is actually stainless as well. The ones you buy from HD or the autoparts stores have a mild steel screw that rusts QUICKLY in our environments. I have several that I got from a boating center that are a couple of years old, and doing just fine. They sit on top of my sump and are exposed completely. They are designed to last years in a boat bilge in saltwater.