Plumbing: Wiping a leaded joint

The traditional leaded joint is a plumbing skill which at one time was essential in any basic plumbing. New, simpler materials, and the disappearance of lead pipework have reduced the need for this skill. A wiped solder joint may still be needed where the domestic cold-water supply comes into the house in lead pipe. A wiped joint may be needed where a stopcock has to be joined to such pipework. Pipework can be continued beyond the stopcock within the house in copper, stainless steel or plastic.

To make a wiped joint, the lead pipe must be cleaned and then belled out to accept a section of pipe or fitting. A smooth, thick, tapered fillet of solder is then built up over the joined ends. Tools needed to bell out the pipe are a hardwood cone or metal ‘dolly’ and a ‘mole’ cloth, for wiping the joint.

Materials needed are: tinning solder, a 450 gramme stick of plumber’s metal, flux, a tin of plumber’s black, and tallow. The latter is used when wiping the joint with the mole.

Before making any connection, turn off the water at the company’s stopcock in the road, or at your own main outside stopcock if there is one.

A hacksaw may be used to cut and trim the lead pipe. The cone or dolly is then inserted. The hardwood cone is tapped in with a hammer. As it is driven in, it should be twisted between blows to prevent it from sticking. The metal dolly, resembling a screwdriver with a rounded tip, is inserted in the pipe and rotated with outward pressure and motion.

Bell out the pipe to a depth of about 38mm. Next apply plumber’s black some 50mm back along the pipe, to stop solder from spreading beyond the limits of the joint. The completed joint should be about 75mm long. A section of either tinned copper or stainless-steel pipe or the spigot of the fitting, also tinned, can be inserted into the belled end of lead pipe. These ends should be similarly treated with plumber’s black, some 50mm back along the tube.

With a shavehook or a penknife, clean both the end of and the inside of the pipe. The outside should be scraped until the metal is bright, back to the line of the plumber’s black. Clean the spigot or the end of the pipe with fine wire wool. The end of the fitting or pipe should be slightly bevelled with a file to facilitate a good fit into the lead pipe.

Next, coat both mating surfaces evenly with flux, tin the surfaces and then bring the two ends firmly together, heating the entire area of the joint with a blow torch. Keep the flame moving to ensure an even distribution of heat and apply only enough heat to melt the tinning solder. Next, apply the plumber’s metal to the joint. Fill up the rim of the belled portion. Apply sufficient heat to melt the solder to a plastic state, so that it does not run off the joint.

Use about a quarter of a stick and then heat the mole in the blow lamp flame and dip it in tallow. To spread the solder around the joint, use a circular wiping action and taper the ends of the joint. You will need to reheat the solder from time to time to keep it workable.

Build up the solder until you have used about 20mm of the stick, then reheat and wipe the joint smooth until the edges are neatly faired.

Do not disturb the joint until it has cooled thoroughly. Take particular care to avoid manipulating the pipework while making the joint or you may fracture it.

10. November 2011 by admin
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