What are the two correct classes of drainage piping?

The classes of drainage piping are categorized based on their functions and the materials used. Soil and waste piping are essential components in plumbing systems. Soil pipes are designed to carry the discharge of toilets and other fixtures, whereas waste pipes handle the wastewater from sinks, showers, and similar sources.

Soil and waste systems are typically distinguished not only by their purpose but also by the materials involved in their construction. For example, soil pipes are often made of materials that can handle the solid waste carried in addition to liquids, ensuring they are durable and resistant to blockages. Waste pipes typically do not carry solids and are often constructed from lighter materials.

The other choices, although certain materials are mentioned, do not represent the correct classification of drainage piping in the same comprehensive way that "soil and waste" does. Understanding the specific function of these types of piping is crucial for designing effective plumbing and drainage systems that comply with safety and health regulations.