Any advice on how to remove year old hard water stains? I got the tank free and so I can't really complain but there are some hard water stains that just don't want to come out. I have tried Vinegar, I have tried Lemon, Lime, small little section of CLR, Lime Away. I have scrubbed, scraped with a razor and still nothing... Any other suggestions? It's all around the top. Here are some pictures it's kind of hard to see cuz I suck at taking pictures but any advice will help.