WC cistern makes funny glug glug noises when filling

[pappyon]

I recently had a new bathroom installed and the WC is the new-fangled type (to me anyway) which has a button thing for flushing the WC fitted on the top of the cistern. It in two parts, and I am led to believe one is for a short flush and the other is the full works.

When the cistern is filling up, you not only get the usual sound of the cistern filling, but a glug glug glug noise which sounds like a lager lout on a Friday night.

I cannot get the top off the cistern to investigate, and would rather leave it alone as I don't want to cause any damage, but would be grateful if somebody would tell my what this funny noise is, and whether it is normal.

 

[bengasman]

It is not normal, but I doubt it will do much harm. If it annoys you, get the installer to look at it.
I always advice against trying to do any diy on things that are under warranty.