live in a 2nd floor flat and have noticed an ‘eggy’, smell comming from what a can only imagine is the sinks.. dont know which plughole smell is comming from as the flat is small and the waft is so stong it ends up consuming every room! Have used caustic soda, bicarb & vin, & loads of other products which only work for a day or 2 before the stink returns. ive taken appart pipes in each room to clean and flat was only built 2 yrs ago by repuitable builder so i cant blame dirty or old pipe work.. problem isnt hot or cold water specific and has only started 3wks ago.. please help!