How to repair, fix and maintain your Grohe
flush system / concealed cistern toilet.
Detailed guide by Avi

Avi Watlow fix

Grohe dual flush / concealed cistern systems are worldwide known for their quality and reliability.
Grohe systems are maintenance free and works for long time without any service.
tipTip: In many countries Grohe warranty is valid for 5-10 years.
You better first check if your warranty is valid and use it prior of following this guide.

After several years of using Grohe system, especially in a high calc level of water (=hard water, = water with high mineral content) and due to material aging, some de-calc, cleaning, maintenance and possibly gasket replacement might be required.
Grohe concealed cistern design is sophisticated and was made so tight that some guidance in needed on how to take it apart in order to perform a cleaning, repair and maintenance process.

When I searched for information on how to repair or take it apart, I have found very little information so I have decided to create my own guide to help you out in the process of taking apart this system. Enjoy it.

Please note:
* This guide shows the Grohe GD2 system, cat. # 38642 000 but it might also help with other models as well.
** In this guide the float valve location is on the left side. Since Grohe system was designed symmetrically, it can be located on left or right depends on your water supply installation.

The process of repairing / maintaining Grohe flush system involves:
* Don't worry, it is easy to gain access to Grohe cistern parts. There is no need to break tiles or wall to do so.
Accessing the system is done through the access panel which is found under the actuation panel.

a: Disassemble according to the following guide.
b: Clean parts from calc buildup, dirt, sand / small stones etc.
tipTip: You can gently brush the parts under running water.
To get into hidden places, best and cheap way is to soak parts in a Citric acid solution.
(use 1 full teaspoon for every liter of water). Citric acid powder can be purchased in every grocery store.
Let it soak for a few hours to remove all calc.
tipTip: When done cleaning and prior to assembling, I advise to test moving parts and make sure it moves freely.
c: Replace any required / fault part.
d: Assemble all parts in reverse order to a. above.

Main parts of model GD2 that needs to disassemble are:
A. Pneumatic actuation plate
B. Water filling float valve
This sub-assembly consists of 2 main parts and additional parts that needs cleaning.
C. Stabilizing bracket (frame)
D. Pneumatic discharge valve (drop-valve)
This sub-assembly consists of 3 main parts and additional parts that needs cleaning.
Its lower part (the rod) holds the silicone seal that opens the water flow of the flush.

Grohe GD2 main parts - general view
* Image shows assembled parts outside the container

Disassembly process:
Note: Clicking on each image will open a bigger image.

1. Take off the actuation plate.
Push the lower part of the plate a bit up (1) and than rotate its upper part towards front (2) to release it and taking it off.
tipTip: Take it off just a few centimeters as 2 air hoses are connected to it.

Actuation plate removal

2. Turn off water supply. Use flat screwdriver and turn it CW

Water supply turn OFF

3. Push the big knob to discharge all water in the cistern.

Discharge water

4. Disconnect the 2x air hoses that connects to the actuation plate. Just pull it straight.
Place the actuation plate aside and keep its front plate from getting damaged / scratched.
tipTip: Mark the actuation plate so you'll know which hose connects to each button connector.

Air hoses disconnect

4.1. Further disassembly of the actuation plate and pneumatic buttons.
This is necessary only if buttons does not function well and if you have the required spare parts (read next)

* Please note that though this plate consists of several detachable parts that can easily be replaced, Grohe does not sell any of it. You'll be offered to replace the full subassembly panel which costs a lot.
Grohe unfortunately does not care about the environment and sustainability matters when it comes to its own parts.
Just in case you got those parts, here are some disassembly images that might help.

a. Press 4x snaps aside
to detach the buttons from the plate

b. This is the detached parts.
Each button is held by 3 Black snaps.

c. Small button parts

d. Large button parts

5. Remove front frame. Unscrew 4x screws and pull frame straight. Use Phillips head screwdriver.

Frame removal

6. Disconnect water supply hose. Turn ring CCW by hand. Move the hose end to the side of the cistern.

Water supply hose disconnect

7. Disconnect water float valve from the stabilising frame.
First push the latch up (1) and while holding the latch, slide the float valve towards the center (2).

Water float valve disconnect

8. Remove the float valve from the cistern.
Do it while turning it along with pulling it out.

a. Pull and rotate
b. Continue to pull and rotate
c. Continue to pull and rotate until removed
d. This is the float valve outside the cistern

8.1. Further disassembly and cleaning of the float valve

a. Squeeze snap (1), pull tab (2) and remove the float (3)

b. Unscrew spring cap

c. Remove cap

d. Remove inner (red) part with membrane (pull out)

e. Unscrew second cap

f. Remove cap and clean inner and o-ring sides

9. Remove stabilising frame.
First squeeze both latches (1) and than pull the frame upwards (2).

a. Release and pull frame

b. Remove frame

10. Remove the pneumatic discharge valve from the cistern.
Separate it to 3 parts while inside the cistern.

a. Turn blue cap CCW (1) and remove it (2)
Let inner seal rod drop down into the container. (3)
b. Remove the pneumatic sub-assembly

c. Remove the seal rod

d. This is the pneumatic discharge valve
Image shows it assembled, outside the cistern

10.1. Further disassembly and cleaning of the pneumatic discharge valve

a. Parts of the pneumatic valve:
Cap (1), Pneumatic sub-assembly (2) and Seal rod (3)
b. Release 3x snaps holding the pneumatic cap.
Pull cap out
c. This image shows the cap removed
d. Remove inner cylinder, pay attention to its slides
e. Rotating handle of the inner cylinder
Make sure handle moves freely
f. This pin moves by small button air push
Blow air through the hose to test it moves freely
g. This small cylinder moves by large button air push
Blow air through the hose to test it moves freely
h. When assembling,
pay attention that this latch goes under the snap

11. Seal gasket. Located at the end of the rod.
If Silicone seal needs to be replaced, this is where you'll find it

To replace the seal, press the 3x snaps, release and pull the outer ring out.

12.tipTip: Clean the cistern container.
If you have got that far, it is advised to clean the bottom of the cistern container.
Insert your hand in the container and pick any stones, sand etc. found in its bottom.
You can turn on water supply and use running water to move and flush any debris found in the container bottom.
Since water goes from the container to the toilet, it is best to take out any large particles by hand to avoid jamming of the toilet water diffuser holes.

Assembling steps:
  1. Insert the seal rod to the cistern. (seal facing down)
  2. Insert the pneumatic subassembly to the cistern and insert the rod inside it using its slides.
  3. Place the Blue cap on top of the rod (6L in front), turn it CW and lock it.
  4. Place the pneumatic discharge valve inside the center pipe, rotate it CCW until it drops down into place and lock.
  5. Insert the stabilising frame. Make sure it is locked into its place.
  6. Insert the float valve while rotating it.
  7. Connect the float valve to the stabilising frame. Make sure you hear the click when it is locked.
  8. Connect the water supply hose.
  9. Install the plate frame.
  10. Turn on water supply. Turn screw CCW. Make sure it does not leak.
  11. Connect the 2x air hoses to the actuation plate. Make sure hoses are not bent and its path is clear.
  12. Install the actuation plate to the frame
  13. Test each button

Voilà, you have completed the repair / fix / maintenance of your Grohe cistern.


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