Geberit Impuls 380AG 3/8" Side Entry Toilet Cistern Inlet Float Valve 244.510.00.1 Push Button Over time as the seat

Over time as the seat is opened and closed

The main difference between traditional UK installations and the current European styles is the syphon / flush valve outlet sizing

Fluidmaster PRO 1/2" Plastic Side Entry Toilet Cistern Inlet Float Valve PRO747UK

1 x Wirquin Jollyfill bottom entry inlet valve

it could very well be an issue with the button instead

Geberit Impuls 380AG 3/8" Side Entry Toilet Cistern Inlet Float Valve 244.510.00.1 Push Button Over time as the seatThere is no need to replace older exposed cisterns just because a filling valve or flush valve system is defective or their water consumption no longer corresponds to state of the art technology. After all, there are appropriate Geberit filling valves and flush valve systems not only for every older Geberit concealed cistern manufactured since 1964, but also for exposed or other cisterns from numerous manufacturers of ceramic appliances. Source: