Toilet keeps filling

Hey guys,

I found that our toilet keeps filling as there is a constant trickle of water from the top of the pan to the pool of water at the bottom. The toilet is the type with a push button flush at the top and a central 'drop valve' type siphon to release the water. When you press the button, a cable pulls the centre part upwards thus releasing the water.

I'm assuming that the sealing rubber ring on the bottom of it this has failed allowing a slow but steady trickle of water to pass through, hence why the tiolet keeps filling. The tiolet was fitted by the previos owner, and so I don't know what make it is, so how would I go about getting a replacment seal? If I removed the unit from the tiolet and took it a to a plumbers merchant, are they likely to stock replacements for these? Or would b&q have them?

The other ppssibility is thatit's overflowing. Water would be going over the top of the central tube in most formats. That would mean the inlet valve's leaking.

Assuming it's the flush valve though, there isn't a standard one. Though you might be able to clean the sealing ring or get lucky by taking it to a merchant, you may have to replace the whole valve.