As feared the old lead gave way, and despite great care I was left with a irrepairable S bend section. I tried
I cut it away and now the problems really start! Luckily a modern plastic S Trap from Wickes fitted the basin screw but the downpipe for this fitting has an outside diameter of 34 mm and the internal diameter of the lead piping was 25mm (probably meant to be an inch?)
I considered all sorts of jointing methods involving bits of car radiator hose, bottle caps, 35mm film cannisters, duct tape (of course) but nothing I had looked fit for purpose - water proof (though low pressure) and not presenting a ledge for further build up of the dreaded gunge.
Step 1: The Ideal Tool ...
In my box of plumbing wreckage I found the ideal item - the shroud from a discarded tap (faucet for the USAsians present).
The picture shows that I've also sorted out some others of different sizes and also that I've paired the up with the valve stem bodies from the old taps. A bit of a cheat that - I had to go and find them after I'd hammered the inverted shroud a little too far down the lead pipe and needed something to extract it!
The wooden dowel is so you can hammer down the shroud below the top of the cut-off lead.
Step 2: Open Wide - This Won't Hurt a Bit!
Step 3: Socket to Me Baby!
I used sliding joint water-pump pliers to gently crimp the top edge of the lead around the plastic to get a good neat-looking joint. The plastic pipe goes into the lead about an inch, and is under very low pressure so I am not intending using any sealing mastic or tape.
I've not shown pictures of the actual creation of the socket - if you're comfortable working with old lead that might split and have the experience then this needs no further explanation - suffice it to say that is was a fraught process and one that I would not have undertaken had the replacement of the whole run of leadwork not been a major job involving cutting into brickwork ,lifting floorboards and trying to route a new plastic waste around an existing soil pipe.
Now - the question that must be asked (if not answered) is why a waste pipe that has functioned perfectly well for over 70 years without blockage gets blocked up with all sorts of gunge after one of the female kind has been in occupation for a little while. Caustic Soda is your friend!