What material should never be used in DWV systems?

In drainage, waste, and vent (DWV) systems, galvanized pipe is considered unsuitable because it can corrode over time when exposed to moisture and wastewater. This corrosion can lead to the pipe's deterioration, causing leaks or even complete failure of the drainage system. The zinc coating that protects the steel from rust can wear off, and eventually, the underlying steel will rust and weaken, making it unreliable for long-term use in DWV applications.

On the other hand, materials like plastic pipe, copper pipe, and PVC pipe are commonly used in DWV systems due to their resistance to corrosion, longevity, and ease of installation. They maintain structural integrity and performance without the risk of degrading quickly, making them preferable choices for effective drainage solutions.