i recopper piped my house about 4 years ago. now i'm getting a bluegreen stain around the waterline of the toilet. its not just a wipe it off stain. there is an actual buildup that needs a lot of elbowgrease to remove. i do have culligan water treatment but not for the toilets. by filling a ceramic bowl from the culligan source and let it sit, i get the same thing. kind of eliminating that being the problem. the water co. says its cheap copper pipe. all the nipples coming out the wall are brass. copper main from the street. any clues?