Making Lead and Oakum Joints in Cast Iron Drainage fittings.



NOTE: Remember to wear appropriate personal protective equipment to work with molten lead. Wear safety glasses and full length shirt and pants of non-synthetic material.

Always be sure to warm tools and materials that are being placed into molten lead remove any condensing moisture which might react explosively.


Cast iron soil pipe joints, also known as calked joints, when made with oakum fiber and lead, are leak-proof, rot-proof, strong and flexible. The waterproofing qualities of oakum fiber have long been recognized by plumbers. Molten lead, when poured over oakum in the hub end of the pipe, completely seals and locks the joint. After the lead has cooled a minute or two, it can be caulked into the joint. The table below lists the amounts of materials needed per joint for various sizes of pipe.



Yarning Irons

Yarning irons are used to pack the oakum into the joint.



Calking Irons

Caulking irons are used to drive the lead firmly into the joint. This is necessary because lead shrinks when it cools. Therefore, to produce a tight seal, the lead must be caulked

to fill the joint.



Inside and Outside Calking Irons

There are “inside” and “outside” caulking irons. Outside caulking irons are used to shape the lead to the inside of the hub. Inside caulking irons are used to shape the lead near the spigot.


Pick out Iron

The pickout iron, (below) has a diamond- shaped flat point, it is used to remove the lead and oakum from a joint.


The lead is heated by a propane flame in a steel pot. Lead is dipped out of the pot and poured into the joint with a ladle.   


When forming horizontal joints the lead is force to enter the space with a running rope which is clamped around the pipe.

Making Vertical Caulked Joints
To assemble vertical, upside-down and hori zontal caulked joints, the plumber should follow these procedures:
1. Wipe the hub and spigot ends dry and free from any other foreign materials. MOISURE CAN CAUSE MOLTEN LEAD TO EXPLODE OUT OF A JOINT. SERIOUS INJURIES CAN RESULT. If necessary, dry the ends with a heating torch to eliminate all traces of moisture.
2. Slide spigot end into the hub of the other pipe and align the joint. A cut piece of pipe has no spigot bead, so extra care should be taken to center the cut end in the hub. Proper alignment is shown in Figure 27.


3. 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, as shown in Figures 28 and 29.
4. 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.
5. 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.
Caulking the lead too tightly may create pressures high enough to crack the pipe. If this occurs, the broken section must be replaced. Refer to Figure 31 for caulking procedures.


Making Horizontal Caulked Joints
1. Prepare the ends of the pipe and pack the joint with oakum as in vertical joints.
2. Clamp the joint runner in place around the pipe and fill the joint with molten lead.
3. After the lead hardens, remove the run ner and trim off the surplus.
4. Caulk the joint as a vertical joint, but use the inside iron first. The entire procedure for horizontal joints is shown in Figure