Gurgling after flushing (Grohe triple vortex)

[Volodja]

Dear all,

Excuse me for my English, as it is not my native language.

I am writing regarding my wall hung Grohe EURO CERAMIC toilet (hung using Grohe Rapid SL frame of course), with triple vortex system. I am very pleased with the product, just one nuisance - the toilet keeps making a gurgling sound approx. 5 seconds after flushing, 7 out of 10 flushes, sometimes quieter, sometimes louder.

I have tried:
1) Disconnecting the water supply, but that does not help and noise stays, so it must not be related to the water filling mechanism.
2) Pouring different amounts of water (1/4 bucket, 1/2 bucket, full bucket, fast and slow) down the toilet from a bucket - that does not create any noise, so problem with drainage does not seem to be at fault.

Please check this video for clarification of the noise and timing: https://drive.google.com/file/d/1nRQ5dVqM6-7HoZ_-RgoQh43C3u1nPi9D/view?usp=sharing

I am guessing that the problem is related to water flowing from the cistern into the toilet bowl, but do you have any suggestions on how I could assess this problem? How do I solve it?

 

[Terry]

It may be a venting issue. The plumbing to the carrier should have a vent tied in before the toilet connection. Normally within six feet. If a bathroom sink is tied into the line, and that is vented, then sometimes that's all you need.

Can you upload the video to YouTube, Vimeo or Facebood and post it using the media setting?

 

[Sponsor]

 

[Volodja]

Thank you for your reply.

But if it was a plumbing issue, should not the noise be present also when pouring water with a bucket down the toilet? As I mentioned - regardless of the quantity of water - the noise persists.

Also, I now tried to manually lift the water release mechanism and if I allow the water container to empty fully - there is no noise.

Uploaded the video in YouTube per your request:

 

[Terry]

That kind of sounds like the fill valve as it shuts off. A bit of a squeak there? I don't think I would worry about that.

 

[Volodja]

Definitely not the fill valve, as this sound persist even with water shut off and I even tried to remove water fill mechanism all together - no luck.
Just make sure to listen till the end of the video, the sound I am worried about is in the last few seconds.

 

[Terry]

Do you have pictures of how this was plumbed?
A vent allows air to pull in which is quiet, but if there is no vent, then it will want to pull water from the bowl.

 

[Volodja]

I can provide pictures later, but it would not make sense, that I can pour 15 liter (4 galon) bucket fast and there would be no noise whatsoever, but when using flushing mechanism even on lowest setting there would be noise.