Final answer:
The statement is true; a lavatory does require a minimum 1-1/4" trap size and is assigned 1 DFU in compliance with the International Plumbing Code.
Step-by-step explanation:
The question pertains to the plumbing requirements as stipulated by the International Plumbing Code (IPC) for a lavatory's trap size and Drain Fixture Unit (DFU) assignment. According to the IPC, a lavatory does indeed require a trap that is a minimum size of 1-1/4 inches (32mm) to ensure proper and sanitary drainage. The lavatory is typically assigned a value of 1 DFU because a Drain Fixture Unit is a measure used to estimate the load on the sanitary sewer system that one drainage fixture represents. The accurate allocation of DFUs helps in the design of a building's plumbing system, ensuring it can handle drainage fixtures if necessary.
Therefore, the statement given in the question that a lavatory requires a 1-1/4" (32 mm) minimum-sized trap and is assigned 1 DFU is true. It's essential to comply with the prescribed requirements to maintain the plumbing system's efficiency and conform to the current standards of the IPC.