How to replace a flush valve in concealed toilet cisterns – Geberit UP200

Geberit 240.638.00.1 Dual Flush Valve

Geberit 240.638.00.1 Dual Flush Valve

As a handyman/plumber, you will come across lots of different toilet systems that you need to repair. From basic ballcock valves and syphon replacements to concealed cisterns where you will in some cases need to disassemble the whole housing unit in order to get to it because the plumber/tiler who installed it never thought about “what if” it needs repairing at some point in the future.

In this article, we’ll show you how to replace a dual flush valve in Geberit UP200 concealed cisterns. These toilet cisterns are usually used in new build apartments and sourcing replacement parts for them can be a bit tricky. Your local Screwfix, Wickes, B&Q and Homebase stores won’t stock spare parts for them. You can always try your local plumbing merchants or get the parts online. If you are in or around Reading, Berkshire and need help with your toilet cistern then contact us. We provide minor plumbing services such as tap fixing and replacement, fix flush and intake valves and much more.

About Concealed toilet cisterns

Hidden toilet cisterns are concealed within the wall or behind a furniture unit, providing a sleek and minimalist aesthetic to the bathroom. They save space and create a clean, uncluttered look by hiding the cistern from view. Operating mechanisms are accessible via flush plates or buttons mounted on the wall. Installation may require professional expertise to ensure proper positioning and functionality, but the result is a modern and sophisticated bathroom design.

Step 1
Remove the flush buttons plate by sliding it to the right and pulling it away from the wall. There will be a metal spring wire on the left-hand side that holds it in place.

Step 2
Remove 2 screws as shown in this picture and remove the holding plate. Try not lose the metal spring bit. If you do you won’t be able to secure the flush plate back in its place once you finish repairing your toilet cistern.

Step 3
First, grab one of the screw holder tubes and rotate it anti-clockwise until it moves freely. Now pull it out just enough so that you can remove the backplate. You can see 2 clips on each side of the box that hold it in place. In most cases, you can just pull it out with your fingers and it will come out if not just use a flathead screwdriver to unclip them then pull it out.

Step 4
Grab the flushing mechanism (see arrow) and lift it up slightly then pull the whole thing out. Now we have enough space to access the flush valve clips and remove it from the tank.

Step 5 (may not be necessary)
If it’s not obvious by now you will need to lift the top cover (usually a wooden decorative board or tiled board) and unscrew the top cover on your Geberit cistern and remove it.  Sometimes you won’t be able to remove the valve through the front hole without removing the inlet valve as well – even then it might be difficult. if you can remove the top cover just do it – it’s so much easier.

Step 6
geberit flush valveNow grab the black clips behind the flush valve with 2 fingers press them together to free the flush valve from the cistern clips and pull the unit out. That’s pretty much the end of it.

The silicon seal cost around £4 (Screwfix) whilst the new valve costs around £25. The valve in question is Geberit 240.638.00.1 Dual Flush Valve for UP200 Concealed Cistern Duofix Frame.

One last tip
Now that you have everything opened and fixed before putting everything back together consider adding a bottle of descaler to your tank and leaving it to work for 12h before flushing. This will descale the float and ensure that it can move freely up and down without getting stuck due to limescale buildup.

You can follow our work on Facebook, Twitter and Instagram.


Handyman category

You may also like


  1. Matt

    Thank you! Just followed this step by step and fixed an annoying constant slow run/refill in twenty minutes, and for the price of a washer.

    • Mike

      No need to take off your decorative top cover.
      The valve unit does come out of the front inspection plate if you are patient.

  2. Handyman Reading

    Thanks, Matt. I’m glad this article helped you. In some cases, you won’t need to replace the whole thing and you can just replace the silicon ring if damaged. The ring costs around £4.50 and you can find it in Screwfix. Another important point to make -if your cistern is overflowing or keeps going after you flush, your inlet valve/float might be full of limescale and it’s getting stuck because of it. You should take it out (very easy to do) and put it in a bucket – add hot water and citric acid and leave it for 10-15min to descale. I’ll update this article with step by step instructions when I get a chance.

    • Esther

      I have a Geberit conceal cistern and since changing my boiler to a combi boiler, the toilet makes a banging noise as the tank refills. Any idea how this could be repaired please?

  3. Danny

    It worked for me. It took me some time to remove the tiled top cover but got there in the end. Thanks

  4. Vicki

    Thanks for posting this. My oh managed to replace the valve thanks to your instructions.

  5. Arnav

    So how do you install a bum-gun or bidet sprayer in a concealed cistern?

  6. Giannis

    Hello…… i would like to ask this….
    I had to change the all the inner parts. A friend of my provided me with a entire Inwall Cistern, so i cant take the parts out from there, and put them in to mine. I took out all the old ones without any problem.
    The problem is that it is impossible for me to take out the Flash Valve. It seems like stuck in there (on the brand new one). Is there any safety trigger somewhere, on the new models that you have to unlock 1st, before pulling it out? Thanks in advance.

  7. Christine Candlish

    would the toilet ever need to be removed to install a new valve even another make valve?

  8. Jim Heaton

    Thanks for the pictures to help with the disassembly. Could not find the Screwfix substitute part until I had got the flush valve out. The Screwfix part is 25438 Replacement Flush Seal for Fluidmaster Dual Flush Valve, todays price £2.49 (out of stock). The Gerberit part number is 816.418.00.1 price today £2.89. The Gerberit stockist had stock, so job done.

  9. Carl-Johan HANSSON

    Dear sir,
    we have an flush valve, but we don’t know the brand. I have an idée that I might be a gerberit, especially when I see the Mounting frame on the picture above, which look exactly the same as ours.
    Is it possible that you give me the size of the Mounting frame, and which flush buttons that fit to this Mounting frame ?