toilet overflow connection to external pipe

[Charnwood]

That collar/nut would have had a sealing ring in it.
You could try to replicate it with a couple of yards of PTFE tape.
Or you could try an 'O' ring.

No guarantees offered for either options.

 

[surd100]

I found an O-ring that, at a stretch, fitted on the overflow pipe. Even with the float valve forced open, the joint now drips only very slowly - a very useful improvement.Thank you Charnwood.

I reckon the O-ring is being pushed onto the 45deg lip at the bottom of the collar and onto the outside of the overflow pipe, by the end of the threaded cistern pipe, albeit rather unevenly - hence the drips.

I'm still very curious to know what the original seal looked like and/or how it was engineered, if anyone remembers or has one.

 

[Charnwood]

Black triangle = missing washer
Blue line = pipe wall
Green lines = nut
Red line = overflow threaded tail

The washer would wedge between the overflow tail and the overflow pipe, pushed in by the nut.

View media item 64841

 

[Terry lambert]

From the picture it looks like you have a drip from where the overflow tube connects to the cistern rather than the overflow itself