How do I remove and replace the piston valve assembly within a toliet cistern? It appears to have a constant leak that causes the cistern to constantly top up the water level. I have isolated the water coming into the cistern, but can't work out how to stop the leak through the outlet valve. Any suggestions would be welcomed, thanks.

Phil in Newcastle, March 2010

push button flush or conventional lever and syphon? either way, really will have to remove cistern to swap syphon

rawplumb, March 2010