What Is a Ductile Iron Pipe?

Mary McMahon

A ductile iron pipe is a pipe made from a special form of cast iron known for durability and flexibility. This pipe is available for plumbing applications in many regions of the world and is suitable for handling potable water as well as waste water for treatment. The development of ductile iron dates to the 1940s, and there are a range of types available for different applications. Manufacturers of ductile iron products can usually produce special order products on request in addition to filling orders with their basic stock.

Man with a drill
Man with a drill

Ductile iron contains distinctive nodules of graphite, instead of the flakes seen in other kinds of cast iron. The advantage of nodules is resistance to cracks and fractures, making ductile iron stronger and more durable. It is also, relatively speaking, more flexible. While ductile iron pipe does not flop like a wet noodle, it is flexible enough to handle pressure from the surrounding environment, for when earth and rock settle over piping, or freezing conditions apply tension to underground pipes.

Manufacturers produce this iron pipe using a method known as centrifugal casting. Technicians pour molten iron into a centrifuge that flings the iron against the walls, evenly distributing it to create pipe walls of uniform thickness. After the pipe cools, it is possible to thread it so it can be screwed to fittings and attachments. Technicians may also line the pipe to help it resist corrosion more effectively.

Lifespans for ductile iron pipe are usually around 75 years, especially if the pipe has a lining and outer coating to address corrosion. Like other cast iron, it can start to rust and develop other problems if it is not kept in optimal conditions. As pipes start to fail, it is possible to pull them out for replacement and recycle many of their components, rather than discarding them. This can make ductile iron pipe an environmentally friendly plumbing option.

Measurement systems for this plumbing product vary, depending on the region. The inside or outside diameter may be used as the basis of measurement. In some regions, the iron industry has a standardized set of measurements companies use for uniformity. Variations in thickness of the walls can be seen to allow pipes to be used in different environments and with different fittings. People preparing for ductile iron pipe installation or replacement should make sure they have pipes of an appropriate size for the conditions.

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