CI Pipe, or Cast Iron Pipe, refers to piping systems manufactured by pouring molten iron into molds, a centuries-old technology. These pipes were frequently employed in the nineteenth and twentieth centuries to convey pressurized fluids like water, gas, and sewage.​

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Cast Iron Pipe (CI Pipe) is a classic, long-lasting piping solution created by casting molten iron in molds. It's been widely employed in pressure pipes and drainage systems since the nineteenth century. CI pipes are sought for their high compressive strength and resistance to root incursion and ground movement, while being brittle and difficult to deal with. Standard sizes and pressure classes (A-D) were described in early British specifications such as BS 78, and legacy measurements are still used in some modern standards. CI pipes, which are commonly used in gravity-fed sewage and stormwater systems, are still significant in DWV applications despite the increasing use of PVC. Hub-and-spigot designs with gaskets or lead/oakum, as well as newer hub less couplings with rubber or neoprene fittings, improve installation efficiency and flexibility.