What diameter is required for a lavatory's waste outlet to comply with plumbing codes?

• A. 1 inch
• B. 1 ¼ inches
• C. 1 ½ inches
• D. 2 inches

Answer: (B)

The required diameter for a lavatory's waste outlet to comply with plumbing codes is 1 ¼ inches. This specification is set to ensure that the drainage system can effectively handle the typical wastewater flow from lavatories without causing blockages or slow drainage. The size facilitates proper waste removal while also accommodating the volume of water that is generally used in lavatories. This standard helps maintain hygiene and prevents backflow or leaks, contributing to overall plumbing system efficiency and safety.

While larger diameters may be suitable for other plumbing fixtures or systems, the 1 ¼ inch size specifically supports the typical needs and design of residential lavatory waste outlets, providing a balance between effective drainage and system integrity.