Which of the following is a listed acid waste pipe material?

• A. PVC
• B. Silicon iron
• C. Cast iron
• D. Copper

Answer: (B)

Acid waste pipes must resist strong, corrosive chemicals and have an official approval for that use. Silicon iron is an alloy specifically developed to stand up to acidic environments and is listed for acid waste piping, meaning it has been tested and approved by the regulatory or listing body for this application. Other materials like PVC, copper, or standard cast iron may not carry that specific listing for acid waste in many codes because their corrosion resistance to concentrated acids isn’t guaranteed or they aren’t approved for that use. So silicon iron meets both the corrosion requirement and the listing requirement, making it the appropriate choice for acid waste piping.