How to Weld Lead

Written by iain mclean
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How to Weld Lead
Seal lead by pasting on layers of solder where needed. (Todd Warshaw/Getty Images Sport/Getty Images)

Lead's principal properties -- water resistance, lack of corrosion, low melting and resetting points -- have made it a useful material to work with. At one time, lead was commonly used to waterproof awkward angles on roofs and for domestic water system pipework. Lead pipe has long been replaced by copper or PVC tubing, however. Untouched, lead lasts for a very long time. So if you have an old house and wish to avoid a major re-plumbing operation, following several basic steps will allow you to weld the lead found within.

Skill level:

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Things you need

  • Cutting knife
  • Wire wool
  • Tin or tube of plumber's flux
  • Fine paintbrush
  • Sheets of glass paper
  • Plumber's blow lamp
  • Canister of butane gas
  • Matches or a lighter
  • 100% pure lead solder, preferably in strips
  • Pallet knife

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  1. 1

    Scrape away the crusty lead around the leak you need to repair or the new join you wish to make using a sharp knife. Thoroughly clean the existing pipe end -- or hole -- and the solder with which you wish to fill it. Brush with wire wool until there is no trace of corroded lead or detritus.

  2. 2

    Apply flux to both the old pipe and the new piece. Flux is an acid, waxy paste that melts upon heating and is used to clean metal surfaces and promote fusion. For small jobs, it is best applied using an artist's paint brush. At the same time, you will also need to prepare a flux coated piece of glass paper for the finishing process. Set this aside for now.

  3. 3

    Light your blow lamp and heat the original piece of lead pipe. Keep the blow lamp horizontal and work around the join or hole in the lead pipe. Heating lead is not like heating copper pipe or other metals.Think of lead as being like butter. If it melts completely, it turns into a dripping liquid. On the other hand, if the lead "sweats," it simply turns soft. You need the lead to be soft.

  4. 4

    Apply the strips of lead solder to the soft lead and keep the blow lamp on it until it also becomes soft. Be careful not to overheat the lead. Maintain the temperature by swinging the blow torch across the area that is being heated. Use a pallet knife to paste the soft lead solder into and around the old lead pipe. The process is a bit like spreading butter onto toast.

  5. 5

    Build up a thick layer of solder -- much thicker than you think you need -- and paste it into the join as you go. When you have done this, remove the heat. Take the piece of flux coated glass paper and wipe the join or patch of surplus lead to get a smooth finish.

Tips and warnings

  • While many building jobs require brute strength, welding lead is more like a craft and should be approached in this way.
  • You can also join old lead piping to new copper tubing; for a watertight join the copper tube must fit inside the lead pipe.
  • You may have seen bulging joins in old lead piping. The reason for this is that lead needs to be very thick to support its own weight and to resist the water pressure that will flow through the pipe.
  • Make sure you have a flat work surface that is located far from flammable materials.

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