Roger Mills wrote:
In an earlier contribution to this discussion,
Cicero wrote:

In the light of
this I think you're looking at the wrong place for the fault. The
fault is probably a defective sealing washer at the base of the
siphon unit where it fits through the hole in the cistern. This is a
thin (about 2 / 3mm) plain rubber washer about 2.25" inner diameter
and a seating diameter of 3.25".

In view of the volume of water being lost you may be able to feel
some wetness at the base of the cistern where it joins the pan as the
rubber doughnut might have absorbed some of the leakage.


You beat me to it - I was going to suggest the same thing.

I think the OP needs to re-assemble the syphon and then remove the
cistern from the pan, support it in some suitable way, and part fill
it with water. It should then be possible to see whether water is
coming out from *inside* the outlet tube (leaking syphon seal) or
*outside* it (leaking syphon/cistern point). I suspect the latter.

I'd suspect the latter as well. I'd remake the syphon/cistern joint with a
dose of LSX.


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk