1. i have the same problem,we have a macdee concealed cistern where you push a button on the wall and an oval rubber inside the cistern will balloon to push up the flush valve mechanism and water will flush down to the twynford pan, it is a year old now and started leaking.
this is what i notice from the cistern; once the rubber balloon push the flush valve up,and flush water, the flush valve will stay up and will not go down to seal the valve seat, so it will continue leaking, i removed the mechanism and clean it and fix it back, but it still leaking, so i removed again the mechanism, i clean the valve seat rubber and the valve seat and fix it back but still it is leaking, again i removed the mechanism, i readjust the height of the rubber balloon (the rubber was attached to a plastic holder where you can adjust the rubber either up or down-beware of the lock, there's one down and two up) return the mechanism back to the valve holder and fill water but still it is leaking, i notice that the flush valve which is fix to the valve seat holder( by turning the flush valve clockwise and there's one lock each side) is moving slightly, i suspect that it is one of the problem, i will try to find a complete flush valve mechanism change the old mechanism, if the leaking stop, fine but if the leaking persist, i have to remove the valve seat holder, the problem is, the cistern is inside the concrete wall and i have to break the wall in order to remove the cistern (next time i will use jacob delafon servo system) by the way, i am a plumbing technician with more than 20 years experience.
fergyleen villareal, October 2010