Cast iron pipes for plumbing

Cast iron pipe is used in most small residential homes for soil piping, which is the main pipes of the drainage or sewer system and leads outside to the sewer or septic tank. The soil stack runs from under the basement floor up through the roof of the house, the top section forming part of the vent system. The size almost universally used is 4" pipe. That size is large enough, and is generally the smallest size available.


The usual fittings used with other types of pipe are cast for use with cast iron pipe, but Y and TY fittings are the ones most often used with cast iron pipe.

How to install

Cast iron pipe is obtainable with threaded joints but that is expensive. Most cast iron pipe is cast as bell-and-spigot type. The plain end, or spigot, slips into the bell end of the next piece of pipe or fitting, is yarned with oakum, and then the joint is filled and sealed with hot lead.

Measuring unthreaded pipe

Unthreaded pipe is caulked at the joints. It is measured in the same way as threaded pipe. There is, however, one exception. You will find it practical to measure short lengths of cast iron pipe from end to end. This is because of the bell and spigot joint used.

Cutting cast iron pipe

Cast iron pipe is cut differently from other kinds of pipe. Use a hammer and cold chisel. After measuring and deciding where your pipe is to be cut, mark a line around the pipe, being sure to make it as square as you can. Support your pipe on 2" x 4"s, and score it lightly all the way around with the cold chisel.

Then make deeper cuts, turning the pipe after each blow. After you have gone all the way around the pipe several times, the pipe will break clean at the point where you have been cutting. Tap the pipe with your hammer at each end, and if you get a clear ring, the pipe is sound. If not, the pipe is cracked and not worth using. Only the piece with the bell is usable.

How to assemble vertical joints

Cast iron pipe is heavy and must be supported while you assemble a joint. Make sure the spigot end of the top piece and the bell end of the bottom piece are clean and completely dry. Place the spigot in the exact centre of the bell and secure both pieces in place with metal strips attached to a framework, so that you do not have to hold them in place. Next, pack twisted oakum into the bell around and around 'until it is about 1" from the top. The bell of a 4" pipe is about 3 1/2" deep, and about 5 feet of oakum will be required for each joint. Pack the oakum in tightly with a yarning iron and hammer.

Now the joint is ready to be caulked with lead. About 3 pounds of lead are needed for each joint of 4" pipe. Melt the lead in a gasoline-fired melting pot and melt enough for several joints, considerably more than you are going to use. When the lead is molten, heat the ladle that you are going to use to transfer and pour the lead.

A cold ladle will chill and solidify the lead so that it will not pour properly. Dip the ladle into the melting pot, scoop up a ladleful of lead, and pour it in the joint without waiting. Keep your head well away from the joint, so lead will not fly out and hit you. Move the ladle around the pipe as you pour, so the lead will flow in quickly all around. Fill the joint completely until a bead forms above the spigot. It will protrude about 1/8" to 1/4" above the rim of the bell.

As soon as the lead cools, caulk the joint with a caulking iron. Lead shrinks slightly when it cools and caulking is necessary to pack the lead firmly inside the joint. Place the end of the caulking iron on the lead and tap the tool gently with a hammer. Striking too hard at first may jar the lead loose from the joint. After tapping lightly all around the joint you can caulk harder. Continue until you are sure the lead has been forced in all around.

In some localities it is permissible to joint cast iron pipe with shredded lead (sometimes called lead wool), which can be caulked cold, or with a commercial jointing-compound, which requires no caulking. That is easier, of course, but molten lead is required in most places.

Assembling horizontal joints

The same initial procedure applies in making horizontal joints as for vertical ones. Secure the two pieces of pipe firmly in place after making sure they are clean and dry. Any moisture might dampen the oakum, causing lead to fly out or prevent it from filling the joint properly.

When ready to pour the lead, first attach a tool called a joint-runner. It is made of asbestos and is attached close to the end of the bell. You pour the molten lead in at the top and it finds its way down and around inside the cavity. After the lead has cooled, remove the joint-runner and caulk the lead in firmly, as with vertical joints.

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