What material should the cleanout plug at the lowest point of the trap for a lavatory, sink, or laundry tray be made of?

The cleanout plug at the lowest point of the trap for a lavatory, sink, or laundry tray should be made of the same material as the trap itself. This practice ensures compatibility and integrity within the plumbing system. When the materials match, it helps to reduce the risk of corrosion and potential leaks that could occur if dissimilar materials are used.

Using the same material also facilitates easier disassembly and maintenance of the trap. Preventing any unintended reactions between different materials is essential for long-lasting plumbing fixtures. If the material were different, factors such as galvanic corrosion could come into play, leading to structural weakness over time.

While other materials like plastic, brass, or stainless steel could theoretically be used in different applications, maintaining uniformity with the trap material ensures optimal performance and longevity.