Steve, they sell mdr (mineral deposit remover) at Wintecs(sorry Mike). It says it works for hard water film so I think it`s the same stuff. Never tried it but I`d be interested to know how effective it is. Have you been aked to remove these stains or are you doing it on your own initiative? I wouldn`t buy something like this unless the job was specifically asked for by the customer and then I`d charge accordingly. Gerry.