I am wondering if it is possible to install a built in cistern next to the toilet. Please see the image attached - the idea is to have a cistern in the short dividing wall next to the toilet bowl. Cistern would be installed in the right angle to the toilet. I am not worried about the gravity drop, as the wall could be slightly taller than what is on the image attached.enter image description here

  • For what purpose? Are you actually collecting rainwater?
    – isherwood
    Jan 31, 2020 at 21:16
  • And the answer is "yes". Did you have a more specific question?
    – isherwood
    Jan 31, 2020 at 21:16
  • 2
    If you're just trying to get the bowl closer to the wall, consider an in-wall toilet.
    – longneck
    Jan 31, 2020 at 21:32

2 Answers 2


You can certainly do it with a separate tank toilet and some inventive plumbing, but the flush performance is going to be worse than a close-coupled toilet, especially modern low flush capacity toilets that have a large flush valve that discharges the water very quickly.

enter image description here

  • This was my first thought, but I'm not sure if you can buy them anywhere these days. I think you're right that a longer pipe might reduce performance.
    – JPhi1618
    Jan 31, 2020 at 21:32
  • They're only found at specialist renovators' supply places, so they're many times the price of a normal toilet.
    – Phil G
    Jan 31, 2020 at 21:37
  • Thank you for your answer. Do you know if the length of the initial vertical pipe as seen on your photo would help with the flush?
    – dvdbrk
    Jan 31, 2020 at 23:38
  • Probably not. Very old toilets had wall-mounted cisterns quite high up, and were waterhogs with dubious flush performance despite being waterhogs. Modern properly designed low-flush toilets (not the early examples where the bugs hadn't been worked out of the designs) do a very good job of flushing with greatly reduced amounts of water and no great elevation. If you are really looking for a "tankless" design visually, you might look into commercial "pressure flush" toilets, though you may need a local pressure tank and some large plumbing to support those in a typical residence.
    – Ecnerwal
    Feb 1, 2020 at 0:23

If you step back from "cistern" you've no doubt encountered "tankess" pressure-flush toilet at most public restrooms, either with a pipe like this, or with a button on the wall and less visible/exposed piping:

enter image description here

In a typical house, you'll need a very local pressure tank and some large supply pipe between to support these things, which are designed for buildings with a much more robust water supply.

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