To replace your diaphragm on a close fitting cistern.
1. Turn off the water supply either by a valve near the toilet, or at the mains & flush the toilet to drain the cistern.
2. Unscrew the cistern from the wall.
3. Look under the cistern. There will be two wing nuts connecting the cistern to the toilet. Undo these nuts and remove the cistern.
4. A large plastic nut will be found under the cistern, which holds the flushing mechanism in place.Remove this nut. it should only be hand tight. (Note where all the washers are.)
5. Take the whole of the flushing system to your local B&Q and ask the plumber there if he can provide you with a new diaphragm or will the whole unit needs replacing.or, if you can ,take the diaphragm out, take that to a plumbers merchant for a replacement.
Keith Howard, March 2006