Which type of pipe is least appropriate for underground drainage piping installation?

Galvanized pipe is the least appropriate for underground drainage piping installation due to several key factors. Over time, galvanized pipes, which are coated with zinc to prevent rust, can suffer from corrosion, especially when buried in moist soils that contain various types of chemicals or minerals. This corrosion can lead to reduced structural integrity, leaks, and ultimately failure of the piping system.

Moreover, the buildup of rust inside galvanized pipes can further reduce flow capacity and lead to blockages. Given these factors, other materials such as PVC, cast iron, and ABS are preferred for underground drainage applications. PVC is lightweight, resistant to corrosion, and has excellent flow characteristics, while cast iron offers durability and strength. ABS is also resistant to corrosion and is commonly used in drainage systems. These alternatives provide more reliable and long-lasting solutions for underground drainage compared to galvanized piping.