Fix lead joint between cast iron and galvanized steel plumbing pipes?
Re-leading the joint isn't too hard.  You will need a slug of lead, a ladle, yarning iron, packing iron, caulking irons, oakum, and torch.  The process goes like this:


Safety first!  Wear thick leather gloves and avoid eating lead particles.
Clean the old lead out
Using a yarning iron, pack the oakum around the pipe. Repeat this operation until the hub is packed to about 1” from its top. Pack the oakum with a hammer and packing iron to make a bed for the molten lead.
Using the plumber’s ladle, carefully pour the molten lead into the joint, as shown in Figure 30. Dip enough lead to fill the joint in one pouring. Allow a minute or two for the molten lead to harden and change incolor from royal blue to a dull grey. Usually, one pound of lead is melted for each inch of pipe size.
Caulk the joint first using the outside caulking iron and then the inside caulk ing iron. The first four blows should be struck 90 degrees apart around the joint to set the pipe. Drive the lead down on the oakum and into contact with the spigot surface on one edge and the inner surface of the hub on the other. Use firm but light hammer blows.


The process isn't really hard at all for vertical pipe, but does require some specialized tools.  If you have several of these joints in your house, it might be worth the investment!

Yarning irons:



Caulking Irons:



Inside/Outside Caulking Irons:



Ladle:



Horzontal Pour: