I have hanging toilets built into the wall from Geberit (like these), which I installed 5 years ago. I only started using these toilets one year ago and noticed the water coming out was pretty dirty. When I opened the back I could see a lot of dirt caked on the inside of the toilet.

I traced this issue back to the fact that this water is rain water, and that the rainwater well had also been stagnant for 4 years (and it probably hasn't been cleaned in more than a decade). There were filters installed for the rain water, but those were pretty dirty and (you guessed it) were not replaced for 4 years.

Is there a way I can clean the inside of my toilet? I replaced the filters already and I am also planning to clean the rainwater well in the summer.

I tried pouring in vinegar, but that did not work, as I think this is organic matter and not some kind of deposit because of hard water. I think I may need to use some kind of bleach, but I am hesitant to do that as I don't know whether my toilet can handle that.

Pictures (not really visible I know):

Toilet bowl with black discolouration

Closer view

  • I'd start with a household cleaner. There are plenty of non aggressive ones that will still help remove dirt over time (you can leave it in the reservoir for a while). If you're not squeamish about these things, you could accelerate the process by brushing off the loose dirt, that way the active ingredients in the cleaner will not be wasted on the easily removable parts.
    – MiG
    May 13, 2022 at 14:02
  • @MiG Please don't answer in comments. Since you seem to have an answer, you should make it an actual answer.
    – Zeiss Ikon
    Jun 13, 2022 at 16:14
  • Plumming is not my area of expertise, this is just how I would do it. And SE can be a pretty unfriendly place where one person tells you off for formulating an answer and the other for probing the issue in comments first. Considering it's been a month and the asker hasn't communicated, I'm also guessing this question is abandoned.
    – MiG
    Jun 13, 2022 at 18:32

2 Answers 2


Whistle While You Work Hack:

Start with a 'pool shock' for the rain water well supply. en.wikipedia.org/wiki/Shock_chlorination …

Then, scour the toilet reservoir with liberal application of 'elbow grease', a plastic pot scrubber, and Barkeeper's Friend - wear rubber gloves and eye protection.

Good luck.


An easier form of chlorination is to use bleach. Do not spill bleach on your clothes, it will most likely remove the dye and there will be pale or white spots on the affected clothes.

Pour bleach some into the cistern of the toilet and let it stay that way for 30 to 60 minutes and then flush the toilet twice. The first flush will deposit what is currently in the cistern into the toilet bowl. The second flush will flush everything away.

Check the results. If repeated treatment is needed, do so.

While all this is happening the bathroom will smell of chlorine. Close the door but open a window and if you have pets or small children keep them out of the bathroom.

Important Safety Message - do not mix bleach and vinegar. Keep the two separate. When mixed toxic chlorine gas is produced.

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