Issue with Geberit In-Wall Tank -- Inadequate Toilet Bowl refill following a Large Flush :(

[VifferFun]

Hi Everyone!

I have two identical toilet setups in two adjacent bathrooms (MainBath and Ensuite):

• Geberit 111.798.001
  
• Toto Aquia CT418FG

I have an issue where the water level in the MainBath toilet bowl after a large flush is too low -- it's only refills to 4" deep (i.e. barely covering the toilet outlet hole), where as the Ensuite refills to 5" deep. After flushing, an inadequate volume of water is being refilled to the MainBath toilet bowl but I can't seem to find any sort of refill adjustment within the Geberit cistern. This issue is very concerning because I can't use my new toilets until this issue is resolved, and replacing the Geberit carrier/cistern would be an enormous effort and cost since the space is completely finished. I have provided videos, diagnostic notes, and some questions below:


Videos:

Diagnostic Notes:

• Toilet Bowl Refill Levels:
  • MainBath, after Large Flush = 4" (too low, barely covering the outlet hole)
  • MainBath, after Small Flush = 5"
  • Ensuite, after Large Flush = 5"
  • Ensuite, after Small Flush = 5"

• The water level in the MainBath and Ensuite cisterns are both at the "fill line" within the tanks
  • Even if I force additional water into the tank past the fill line (by pressing down on the float), the MainBath toilet still only refills to 4" following a large flush
  • This implies that the water level in the tank is not the issue

• I can use a watering can to manually trickle water into the MainBath bowl to increase the bowl water level from 4" to 5"
  • This implies that the toilet's S-bend is not an issue

• If I do a large flush in the Mainbath and continue holding the button, it will allow some additional water into the toilet and it will refill to 5" (but this isn't normal operation)

• I tried removing the MainBath actuator plate and button assembly to manually flush the toilet by pulling up on the stopper
  • The problem persisted -- the bowl would only refill to 4" following a large flush
  • This implies that the length of the buttons is not an issue

• It seems that the MainBath water level will refill to 5" after a small flush, but only fills to 4" after a large flush:
  • You can see it in the video, but the MainBath toilet has a loud "gurgle" sound at the end of the large flush (since the toilet bowl pretty much empties entirely); the Ensuite toilet doesn't do this
  • Since the MainBath toilet empties completely during the large flush, it requires more water to refill the bowl compared to the Ensuite toilet; however, the toilet bowl refill ends after the same short duration for both toilets (which I believe is why the MainBath only fills to 4" instead of 5")
  • When doing a small flush with the MainBath, the bowl doesn't empty entirely (so I think this is why I don't have the water-level issue after a small flush)

Questions:

1.) Any ideas on what could be the issue?

2.) Standard toilets have a refill tube/hose that discharges water into the overflow tube for a period of time following a flush. How does the Geberit refill the toilet bowl? How can I adjust the refill rate so that the Geberit matches the refill requirements of the toilet?

3.) Is the sound (of complete water discharge) at the end of the MainBath flush "normal", or should it be quiet (i.e. not completly discharging) like the Ensuite?

Thanks!

 

[Terry]

Can you upload the video to youtube and then add the links as media?

 

[Sponsor]

 

[VifferFun]

Hi Terry,

Thanks for the suggestion! I've uploading the videos to YouTube and edited the original question so that the videos are now embedded. Hopefully a pro out there can help me out

Thanks!

 

[PlumbSolve]

I doubt its the geberit mechanism. Could it not be a venting issue or caused by a restriction in the pipe. Ive seen this happen on pipes that have been partially clogged.