Torn or damaged diaphragm. Turn off water. Unhook flushing handle. Undo big white lower nut on syphon and slide syphon body up towards top of cistern. May have to move flush handle and/ or the inlet valve float to give enough room to get the body out. Once out, unhook flush link ( metal bit that joins handle to plunger which is inside the syphon body )Then withdraw diaphragm holder from bottom of syphon and examine diaphragm ( blue or clear, thin plastic ) for damage. If torn or frayed this will affect syphon action. Slide remains of old diaphragm off it's holding rod, after lifting a small clear plastic tab with two holes, which keeps the diaphragm in place. Clear any limescale and, if available, grease the sliding area of syphon with a little silicone grease. Replace with correct shape diaphragm( some are D shaped. ) in a reversal of the removal process.
pat, December 2010
