Final Answer:
The minimum floor drain trap arm on a 3" drain should be at least 2 inches.
Step-by-step explanation:
When dealing with a 3" floor drain, the minimum trap arm requirement is crucial for effective drainage. In plumbing, the trap arm is the horizontal pipe segment between the trap and the vent. For a 3" drain, it is recommended to have a minimum trap arm length of 2 inches. This measurement is essential to ensure proper drainage, prevent sewer gas escape, and maintain the integrity of the plumbing system.
A sufficient trap arm length allows for the effective functioning of the P-trap, a curved section of the pipe that holds water to create a barrier against sewer gases. In the case of a 3" drain, the 2-inch trap arm helps maintain an optimal water seal in the trap, preventing the backflow of gases and promoting smooth drainage.