hi I have a concealed toilet cistern (white square box) with a dual flush push button and I can get access to the float.

The problem is that after a big flush the water keeps running at significant speed - so much that it is emptying as quickly as the mains can supply.

I suspect it being a mechanical error more than a leak as a little flush does not cause problems and the toilet water is not otherewise running.

Michael, September 2007

Generally this is a flush fault, the syphon is not seating properly, make sure the float stem in vertical and not catching any where, rem to release the button one second after its been pushed, this should alloy the syphon to reset

Norman, September 2007