Push button toilet flush

[sadders]

We have a push button toilet flush with the cistern hidden behind a tiled unit.

The button is a bit stiff for a start but the main problem is about half the time it is flushed the syphon doesn't seem to properly engage and we get a continuos trickle into the pan until it is flushed again. The rest of the time it flushes normally.

Recently it improved. The rest of the sink plugs in the house were draining slowly so I sluiced out the outside drain. This improved the plugs but the flush started playing up again. I can't see how these two are connected.

Any ideas?

 

[LUNAT]

HI

sink waste and flush not connected.flushing valve rubber seal worn or an object stuck which prevents complete seal and water over flowing into the pan.