"A blot on one's escutcheon" used to mean a stain on one's reputation, because escutcheon also meant an emblem bearing your coat of arms. Well, if you're not into heraldry you can still get lots of escutcheons!
The link above will take you to the site to choose the ones you need. As the video will tell you, make sure to measure the pipe correctly. If you don't want to unplumb anything, get the kind that just clips around the pipe.