I have a couple of concealed slimline cisterns.
They have started to leak water into WC, this is 100% not down the
overflow pipe, as water level is well below that.
Took it out cleaned all €¦ still the same (or worse if anything) €¦. From
empty the infill €˜torbeck type starts filling, all is fine until
around 50mm deep .. and the water starts to leak €¦. Assuming that the
bottom €˜main seal is OK, as nothing gets past that initially, only
leaks when it get in over the float, so my logic is that is must be
getting past the inner seal.

Are these spares items ?
The main seal aprox 66 OD and 48 ID has No. 14.11.29 1 DAL
The inner seal aprox 48 OD and 30 ID has No. 14.11.30 8 DAL

Picture shows siphon, and the seals in the lower picture.
http://www.mediafire.com/file/p7yqjk...iphon.pdf/file