Cast Iron Pipes (CI)

Published: | Updated: August 24, 2020;

Definition - What does Cast Iron Pipes (CI) mean?

Cast iron (CI) pipes were widely used for the transportation of water and sewage before plastic pipes were invented. They are one of the oldest piping systems present today and are now being replaced by high-density polyethylene (HDPE) pipes and polyvinyl chloride (PVC) pipes. Some cast-iron pipes are still in working condition, but most have deteriorated and are in need of replacement.

Cast iron pipes have a lifespan of 75 to 100 years, but evidence shows that some have lasted much longer. Cast iron pipes can handle low wastewater pressures even if the corrosion has occurred because of the thickness of its walls.

Though cast iron pipes corrode over time, the rust forms a layer over the remaining pipe that slows down corrosion. The benefits of cast iron pipes still make them a good choice for installing in homes, but with cheaper and less tedious options now available in the market, cast iron pipes are less preferred.

Trenchlesspedia explains Cast Iron Pipes (CI)

With thick walls and long lifespans, CI pipes installed in the 19th and early 20th century are often still in good working condition except for portions of damaged pipes that need replacement. People who have built homes prior to 1970 have cast iron piping installed, and most of them are satisfied with its performance. Its long lifespan, durability, ability to withstand heavy loads/ high-pressure, and its sound deadening properties made it a popular choice in the 20th century.


Problems with Cast Iron

Cast iron pipes provide a water-tight seal and protection against root intrusion and can withstand severe ground movement such as in an earthquake, but rust and corrosion are its greatest problems. As corrosion sets in, the pipes become weak, and severe corrosion can also cause the collapse of the pipe, leading to additional problems.

Over time, the interior of the cast iron pipe begins to rust as it continuously comes in contact with wastewater. This eventually leads to a buildup of rust and a consequent reduction in the hydraulic capacity of the pipe. The rust will also create a rough surface that reduces its flow velocity.

Wastewater flow through a cast-iron pipe can also etch a channel at the bottom of the pipe over time if left untreated. This can lead to wastewater escaping the pipe from the bottom and eventual collapse.


Rehabilitation of damaged pipes

As cast iron pipes reach the end of their serviceable life, it is necessary to rehabilitate them. The pipeline is first inspected using robotic crawlers, and problem areas are identified. If the structural integrity of the pipe is intact, liners can be used to line and create a new interior that is as good as a new pipe. Trenchless rehabilitation techniques utilize high strength liners to rehabilitate damaged pipelines such as cured-in-place-pipe (CIPP), fold and form, and thermoformed type.

If the pipeline has lost its structural integrity, it will have to be replaced. Trenchless rehabilitation methods such as pipe bursting and slip lining can be used for this purpose. One advantage of trenchless repair and rehabilitation of cast iron pipes is that the intact portions can be left untouched while only the damaged portions are repaired. This also reduces the overall cost of rehabilitation.

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