Cast Iron pipe is widely used for city water-distribution systems because of its high resistance to corrosion and consequent long life. Cast iron pipe is made from pig iron. Such pipes are normally made from 5 cm to 120 cm in diameter.Under normal conditions, a cast iron pipe can be expected to last 100 years.

The usual length of a pipe section is 12 ft, but lengths up to 20 ft can be obtained. Cast iron pipe is made in several thickness classes for various pressures up to a maximum of 350 psi.
Cast-iron pipes are usually dipped in a bituminous compound for protection against corrosion and to improve their hydraulic qualities; larger sizes may be provided with a lining of cement mortar. A common joint for cast iron pipe is the bell and spigot. A few strands of jute are wrapped around the spigot before it is inserted into the bell, and then more jute is packed into the joint.

Finally, the space between the bell and spigot is tilled with a molten lead, which is tightly caulked into the joint after cooling. Patented compounds of sulfur and other materials and neat cement mortar are also used for joints. These materials are cheaper than lead, but the joints are usually less flexible. The flanged pipe is used for pumping stations, filter plants, and other locations where it may be necessary to disjoint the pipe. Flanged couplings must be fitted perfectly and provided with a gasket if they are to be watertight. Because of the skilled labor required for lead joints, numerous mechanical couplings are finding extensive use and have largely replaced bell-and-spigot joints. These couplings are bolted together and designed to avoid the careful fit required of ordinary hanged couplings and to permit flexibility in pipe placement. One of the most common is the Dresser coupling.
Cast iron pipes are also cheap and economical. These pipes can be joined easily and can be cut and bored easily too.
They are durable up-to 100 years of life but, as time passes, their strength of carrying water decreases. They cannot bear pressure more than 7 kg per square centimeter: The cast iron pipes are generally cut with chisel and hammer, but for a better cutting cutter and hack saw can be used.
Following methods are used to join a cast iron pipe.
(i). Bell and Spigot Joint.
(ii). Hanged Joint.
(iii). Expansion Joint.