For sewer systems, which is an acceptable material for pipes?

In sewer systems, both cast iron and PVC are widely accepted materials for pipes due to their durability, resistance to corrosion, and ability to handle the specific requirements of wastewater transport.

Cast iron pipes have been used for many decades in sewer systems because of their strength and longevity. They can withstand high pressure and are resistant to damage from shifting soil, making them suitable for underground applications. Their sound-dampening qualities also help reduce noise from flowing sewage.

PVC, or polyvinyl chloride, is a more modern option that has gained popularity due to its lightweight nature, ease of installation, and resistance to chemicals often found in wastewater. PVC pipes are less likely to corrode and can be joined using solvent cement, making them quick and cost-effective to install.

While copper is recognized for its antimicrobial properties and is sometimes used in specific plumbing applications, it is not commonly employed for sewer systems due to its high cost and susceptibility to corrosion in the presence of sewage. Therefore, the combination of cast iron and PVC as acceptable materials for sewer pipes makes the option that includes both B and C the best choice.