I have a newly fitted wall hung toilet with a concealed cistern. There was a dribbling/hissing sound coming from the cistern. I can remove the worktop-mounted dual flush plate and view the inside of the cistern from above through the cut-out in the worktop.
I can see where the leak is coming from (the joint between a flexible pipe connector and a threaded pipe inside the cistern), and I can see that the water is overflowing down a central pipe/plunger valve. I presume that this is an internal overflow.
But where is the water exiting when it flows into the overflow? Reading this forum, I gather that internal overflows flow water into the WC pan. The water in my pan is undisturbed, and I see no sign of any water seeping into the pan. There is no external overflow.
Can anyone cure me of my ignorance?