What is the primary material used for sewer lines?

The primary material used for sewer lines is PVC or cast iron. PVC (polyvinyl chloride) is widely favored in modern plumbing due to its lightweight, corrosion resistance, and ease of installation. It has become a standard choice for residential and commercial sewer systems.

Cast iron, on the other hand, has been used historically for sewer lines due to its durability and ability to withstand high pressure and heavy loads. While it is heavier and more expensive than PVC, it offers longevity and sound-dampening properties, which are beneficial in certain application contexts.

Both materials are widely used in the construction of sewer lines depending on the specific requirements of the installation, which can include factors such as environmental conditions, load-bearing requirements, and local building codes. In summary, PVC and cast iron represent the predominant materials in sewer line construction, hence making this combination the correct answer.