Which material is commonly used for drainage pipes in plumbing systems?

Cast iron is commonly used for drainage pipes in plumbing systems due to its durability and strength. It is resistant to high temperatures and can handle heavy loads, making it suitable for carrying wastewater and sewage. Cast iron piping systems are known for their ability to reduce noise from flowing water and are often used in commercial buildings and applications where performance and longevity are critical.

Other materials, such as CPVC, PEX, and polyethylene, have their specific uses in plumbing but are not typically employed for drainage. CPVC is more suited for hot and cold water distribution, while PEX is flexible and often used for residential water supply lines. Polyethylene is commonly used for water service lines and certain drainage applications, but it lacks the structural integrity and sound-dampening characteristics of cast iron for drainage purposes.