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.

  • I'm voting to close this question as off-topic because is asking for product recommendations.
    – Just Do It
    Mar 7, 2016 at 16:24
  • I specifically asked for main/active ingredients, not products. Obviously you need a "product" (as in chemical substance in the broad sense) recommendation for this problem. Mar 7, 2016 at 16:42
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    I'd like to have this question reopened. I only recently solved it after trying 10+ expensive products, I think it is really a "life hack". The magic answer is HCl (hydrocloric/muriatic acid) available in hardware stores. Usually you can get 20-30%. It is scary compound, and you need to use rubber gloves (not latex) and eye protection. Remove all the water (w sponge), and fill the siphon. LEAVE THE ROOM WELL VENTILATED AND GO AWAY, the fumes are noxious. Every 10 minutes use a brush to scrape the scale a bit, 3x. Flush, multiple times. Only use if toilet is ceramic and fittings are plastic.
    – xmp125a
    Feb 9, 2019 at 19:11

1 Answer 1


Hard water scale can be removed by acid. White vinegar is a weak acid and may work, given time. Weak phosphoric acid as in a 2l bottle of cola may work too.

Strong acid such as ~30% muriatic (HCL) sold in home improvement stores may corrode fittings and could cause other problems

  • Do you have personal experience in removing "age-old" scale with any of these products? Mar 7, 2016 at 16:45
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    Yes, the first and last I have used personally. The area of Southern Ontario I lived in had very hard (but good) water. Bathtubs and kettles quickly got scale and toilets would get scale around the water line as well as lower. Of course if it's 2mm thick it's going to take time or strong medicine. Mar 7, 2016 at 16:51
  • "The last" as in HCl? Mar 7, 2016 at 16:54
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    Yes, hydrochloric acid, and I had the problems I mentioned. More dilute solution would be better but I don't recommend it- aside from corrosion and personal danger if you get enough exothermic heat from the dilution you could crack the toilet bowl. Mar 7, 2016 at 16:57

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