Now this job should be simple right? No, not for me it's driving me potty. Any advice to solve this will be gratefully received.
The cistern is a Twyford standard close coupled cistern with a conventional syphon fitted about a year ago.
A few days ago the overflow pipe (exits into the common waste) was found to be wet and the carpet underneath it, damp. Diagnosis is that the float valve was still letting water into the cistern and probably needed a new diaphragm fitting, as adjustment of the arm didn't work.
After 3/4 days of trying to fix this, no change. Have fitted the diaphragm in both directions (don't think there's a right or wrong way is there?).If I adjust the float arm to shut off to avoid overflow, it takes an age (about an hour) for the cistern to fill up to the required level - at the beginning of the fill all is OK but before you get to half the fill level, the flow reduces down to almost a trickle and just about shuts off nearly an hour later.
I have cleaned and removed all lime scale from all parts of the float valve, fitted a new flat washer behind the valve itself (this stops water going out through the screw-on coupling that holds the valve together), and replaced the diaphragm.
The float itself is not getting stuck and the whole thing should work OK. But I must be missing something.
I'm heading for a breakdown with this - help!