I ask this question here because all other sites I found on the web (mostly in German, because this does not seem to be a common problem in the English-speaking world - or people just don't care) give a lot of suggestions but do not seem to agree on one that actually works.
I have toilet elbows that are covered in urine scale of different ages and thicknesses. One is just various shades of dark yellow to brown, the other is black. Both seem to result from very hard water and the lack of proper cleaning for approximately ten years. The scale is only present on the surfaces that are constantly covered with water.
I have tried dishwashing tabs and powder, no visible improvement.
Which product/approach have you successfully used to remove urine scale of the given "badness"? I'm wording the question this way because I do not want suggestions of what might possibly work just because chemistry says so, but which you haven't actually tried yourself.
If you specify certain products, please make sure to include the main ingredients because brand names vary between countries.
PS: After the question received a downvote for lack of effort, I would like to add: I found hints on several sites that included citric acid, vinegar (concentrate), phosphoric acid, nitric acid, sulphuric acid, hydrocloric acid, TNT, antimony pentaflouride, probably some other acids I forget about, combinations of acids and heating, dishwasher tabs, denture cleaner, abrasive materials, buying a new toilet.
Some of the sites are notorious for low quality answers IMHO, and very few of them hinted at actual personal experience, neither did they state how bad the scaling was in their case. That is why I came here, because in my experience SE yields answers of very high quality and reliability.
PPS: I am pretty sure that TNT and antimony pentaflouride work, but those materials are hard to acquire, dangerous to use, and would most likely result in having to replace the toilet anyway.
PPPS: As this question was put on hold because it is not about thinking "outside the box", I'll be happy to accept answers that have an out-of-the-box solution to my problem. As I said, TNT as more of a mechanical than a chemical solution is slightly outside the box, but probably not practical.