Why is cast-iron pipe commonly used for underground service?

Cast-iron pipe is commonly used for underground service primarily due to its excellent resistance to corrosion. This characteristic is crucial for underground installations, where pipes are exposed to moisture, soil conditions, and various chemical influences that can lead to deterioration over time. The inherent durability of cast iron allows it to withstand these harsh environmental factors, making it a reliable choice for sewage, drainage, and other underground piping systems.

While other materials might be lighter or cheaper, the long-term benefits of using cast iron, particularly in terms of longevity and reduced maintenance needs, make it a preferred option for many plumbing contractors. Its ability to resist corrosion significantly contributes to its performance and reliability in underground plumbing applications.