Getting lime, calcium & rust off ceramic tile




So we just purchased a house that has a large ceramic tile shower. The water where we now live is incredibly hard and has left calcium and lime buildup along the shower walls. I've tried everything from LimeAway, lemon juice & white vinegar (pre-treated with baking soda) and barkeepers friend. Someone suggested phosphoric acid but after reading about that stuff it scares me. Any suggestions on how to clean or recommendations for the best shower tile cleaners?

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I had scale on an uneven tile on my floor from puppy wee. Tried everything until above commenter mentioned borax. Of course!! How stupid of me to forget. Ran to the spot, sprinkled the borax on wetted tile and rubbed with my shoe sole. Gone in 1 minute!! Thanks