The flap valve needed replacing so I've done the sensible thing and
fitted a two part syphon, which works fine. (And will make replacing the
flap valve a two-minute job in future.)

However, there is a persistent drip from the bottom of the cistern,
coming off one of the bolts which holds the cistern to the pan. I
suspect that the hole in the bottom of the cistern where the end of the
syphon comes out is larger than normal as when I took the old syphon
out, there was some brown rubbery sealant type stuff filling the gap
between the syphon pipe and the edge of the hole, between the black
washer inside the cistern and the nut on the outside. I showed this to
the man at the plumbers' merchant and he said I shouldn't need anything
like that, the washer on its own should make it watertight. I've got a
new close couple plate and doughnut washer, but even with the old brown
sealant gunk replaced where it was, I still get a drip. Do I need new
sealant, if so, what sort? On the instructions for the new syphon, it
says, "No sealing compound, paste, flux or solvent to be used with
plastic or rubber surfaces to avoid damage."

Alternatively, is it possible that the leak is just happening because I
haven't got the syphon nut tight enough? I've got it _very_ finger
tight, but haven't got a big enough spanner to do it any further. Is
there a standard size for the hole in the bottom of the cistern? The
previous occupier liked to do things in non-standard ways (electrician
said we were lucky to be alive, but that's another story ...)

Thanks for any help.

- guy

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