Introduction: Joining Plastic Waste Pipe Into Old Lead Pipe

Having tried to clean out an old sink waste pipe with coat-hanger wire and caustic soda and failed I tried ever so carefully to unscrew the drain plug at the bottom of the S bend after clearing away the generations of paint, dust and general gunge.

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 ...

Sometimes at car-boot sales one sees old lead-working tools - hardwood mallets, cones and suchlike - but I've never added to my collection and rather than turn up something (which would have meant repairing the lathe anyway!) looked around for suitable things which I might be able to hammer into a heat-softened lead pipe to stretch the bore.

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!

I gently warmed up the pipe with a propane torch and was able to tap town the smallest cone without splitting the pipe. Encouraged I followed up with the middle sized one and then alternated between the two until I had made a well shaped socket at the top end of the pipe. I constantly checked the opening with an off cut of the 34mm plastic pipe I was going to connect.

Step 3: Socket to Me Baby!

Job done! The correct length of the 34mm pipe was cut and forced down into the lead and all the upper joints positioned tightened.

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!