u/DigSmall4896

Hi everyone, the toilet in one of the properties I manage is making this really loud sound when flushed, not all the time but regularly.

Does anyone have any idea what could be causing it?

My friend who’s a plumber has changed the float valve and flush valve to see if that made a difference but it’s still doing it and he’s at a loss and gone back to think about it.

I was wondering if anyone in here could think of what could be done to fix it? Thanks in advance