Close coupled cistern leaking into pan, not the normal reasons!

[Ziggles]

Hi all,
So CC toilet and a fair amount letting thro into the cistern, changed the syphon and it’s still going it. Whilst looking at the near empty cistern ( water level beneath the flange the siphon sits in ) and it’s still letting through. So cistern off, and replaced the whole arrangement with new washers and donut. It’s still letting through!
I can only assume that there is a crack in the cistern at the base of the flush valve?!

 

[Wayners]

Take cistern off.
Stand in a bucket and fill with water to test for a leak.
I'll add...
Don't over tighten the fittings. The close couple nuts and bolts just need nipping up or you will crush the rubber washers.
Same goes for Syphon.
Its should not leak if you tighten with your hand so you only need to go a little further. There is no water pressure.

 

[blup]

What make of flush valve? Some like the Tomas Dudley need to turn and click in place or they will let through.