Help please! Leaky toilet!

[SarahBoo]

Hi! Grateful for any help or advice please. I have an armitage shanks push button toilet that has a constant flow of water down the back of the bowl. I've tightened up everything in the cistern but that hasn't really helped.

I've read online that it could be the seal on the flapper (the water here is very hard) but I've no idea how to get to it! Pic below, any ideas of how I remove the big white bit in the centre great fully received as I can't seem to get it off.

Thanks!
Sarah

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[SarahBoo]

Typically, just after posting I found the tiniest writing on the unit that says 'twist to access seal'. Got it and the rubber has completely disintegrated so pretty sure I've found the problem!

 

[HERTS P&D]

See below:

http://www.shop.lunns.net/flush-valves-14-c.asp

or have fitted a new push button syphon:

http://www.screwfix.com/p/fluidmaster-button-cable-dual-flush-bottom-inlet/58353

Change the float valve while the cistern is off.

Andy