Noise after my neighbours above me flush the toilets

Hi Marco. Well from the sound of it your waste traps are being emptied by suction from the loo being flushed & if it has only just started doing this it is indicative of a blockage somewhere. You mention a gulley however with this scenario I would expect your waste pipes to be delivering into a soil pipe. Normally there would be an open vent or air admittance valve to prevent this happening which may have a blockage preventing that, hence trying to scavenge air from your traps. Another cause could be a blockage down line. Air & sewage gets pushed up your waste pipes before then subsiding. If your wastes are delivering into a gulley outside then you could have a similar thing as the latter, where if the wastes are going down below the gulley edge & a blockage is causing the gulley to overflow, then the pressure would cause your traps to gurgle. In either case it sounds like a blocked foul drain which needs to be cleared. Should the problem persist, you might consider fitting anti-vac traps or inline air admittance valves on the waste pipes. My thoughts are that as it has not always done this that drain clearance should provide the solution. Hope this helps.

Hi If it only happen when flushing the wc Sounds like the wc Inlet pipe need changing replace the valve it shld ok