ideal standard dual flush toilet cistern keeps on filling up with water even when it has reached the level.

M Robinson, November 2011

One of two things
1st: The float arm might need adjustment providing the float ball has not got water in it. If the float ball has no water in it then adjust the other end which closes the inlet valve. Undo the pin lock nut turn the pin toward the valve pin about 3 full turns. Flush toilet and wait for cistern to fill see what level the water shuts of at. If after all adjustments prove no solution then>
2nd The inlet valve washer needs to be replaced.

bb, November 2011