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.

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.
 Tip: 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.
 Tip: 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 the disassembly steps.

 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.

12.  Tip: Clean the cistern container.
If you have got that far, it is advised to clean the bottom of the cistern container. Insert your hand into 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.

 Tip: In order to keep the shiny chrome coating of the actuation plate and buttons for years to come, DON’T use any toilet cleaner or any other aggressive cleaning material. Use only a soft paper towel with some window cleaner that contains Alcohol to clean and disinfect it.

 Tip: Clean the cistern periodically.
Once a year or every several years depends on the water hardness level in your area.
In many places the water is hard and scale will build up on the cistern parts which eventually will cause it to malfunction.

Tip: A common fault is water overflow. The water supply does not stop when the cistern is full. The cistern is still functioning but the water supply keeps flowing into it. Because of an overflow safety design, the excess water flows to the toilet. The reason for this fault is that the clogged float can not move freely and the valve that controls the water supply will not cut off.

To solve and fix this fault, disassemble the parts as described above. Soak the parts for several hours in a water with citric salt solution. Use also a soft brush to remove any stubborn hard scale. Brush all parts and make sure that the gasket seal and its area (see part 11. above) is sooth and scale free. Pay close attention to the membrane (see part 8.1 d above) and make sure it is not damaged and that it is assembled correctly. This small gasket is responsible for cutting off the water supply when the float goes up.

When done, rinse all parts and reassemble it.

Enjoy, Avi Schneor 
* For Hebrew intro, follow to this link

Comments, remarks and updates are welcome.
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